When Are They Anusim (Crypto Jews)? some Clues and Hints

1. They have uncommon surnames. According to JewFAQ, "One reason for the frequency of German names among Jews is a 1787 Austro-Hungarian law. The Austro-Hungarian Empire, which controlled a substantial part of Europe at the time, was the first country in Europe that required Jews to register a permanent family surname, and they required that this surname be German. A copy of the decree can be found on the Polish-Jewish genealogy website, Shoreshim. This explains the frequency of German surnames in Western Europe, but it doesn't explain the frequency of German surnames for Jews in the Russian Empire, where German surnames for Jews are also common. The frequency of German family names among Russia may be due to migration from Western Europe." (http://www.jewfaq.org/jnames.htm) In Russia, surnames were not required until 1804. "In the Austrian Empire, which ruled much of southern and eastern Poland, Jews were ordered to take such names in the 1780s and ’90s; in Germany, in 1797; in tsarist Russia, in 1804." (http://forward.com/articles/13721/how-did-jews-choose-their-last-names-/#ixzz2cWvkzAwz) In order to comply, some Jews--especially Anusim--made up or took gentile or gentile-sounding names to pass at least the lines of acceptability, assimilation, etc..
2. A gentile name doesn't necessarily mean that they are gentiles. In fact, "Jews living in gentile lands have historically taken local names to use when interacting with their gentile neighbors. Anyone with a name that is hard to pronounce or to spell will immediately understand the usefulness of this! The practice of taking local names became so common, in fact, that by the 12th century, the rabbis found it necessary to make a takkanah (rabbinical ruling) requiring Jews to have a Hebrew name!" (ibid.)
3. Baptism records don't show up too much before 1700, if at all. In fact, for example, Slovakian baptism records "Many church books from earlier time periods were lost during the Turkish invasions and Slovak rebellions around 1600-1700. Those which carry over past the early 1900's (even though they may have begun earlier) are still located in local city halls or other institutions. The Family History Library has copies of almost all birth, marriage, and death registers for the following religions: Catholic (the majority religion), Evangelical Lutheran, Reformed, Jewish, Greek Catholic, and Orthodox. Filming of the records was done from 1991-2009. The images in this collection are from those films." (https://familysearch.org/learn/wiki/en/Slovakia_Church_and_Synagogue_Books_(FamilySearch_Historical_Records)) Also, "Starting in 1869, the civil authorities took charge of keeping records of births, marriages, and deaths, although the individual churches continued to actually record these events. The official legal copy was kept by local officials. This action was prompted when many of the clergy refused to perform Catholic rites for non-Catholics. Everyone was registered under this new system (not only Catholics or Protestants)." In fact, Andrew Rusna's granddad had to be "acquitted to marry" because his conversion was not believed to be geniune--he had to go through a dispensation to maintain his Anusi Yahadut (Crypto Judaism).
4. Religious freedom was really nominal in any given state for at least the commoner, even in de jure terms. Also, gentiles could not convert "down", though Jews could (and often had to) convert "up". According to Wikipedia, the story of Count Potocki could not be true. "There is some evidence that the Potocki legend is an embellishment of a true story. A report published in the July 1753 edition of The London Magazine describes the story of a very similar execution. The correspondent dated his report June 11, two days after the end of the Shavuot holiday. It describes "an apostate named Raphael Sentimany, a native of Croatia", who converted to Judaism and adopted the name Abraham Isacowicz." (http://en.wikipedia.org/wiki/Abraham_ben_Abraham) Also, "Tazbir notes that the tragic fate of Potocki, passed through Jewish oral tradition, remains unconfirmed by 18th–century Polish or Jewish primary sources and that there is no evidence in any archives or genealogy tree that Potocki existed.^[7] He also notes that the Polish nobility was guaranteed the freedom of faith (by acts like Neminem captivabimus and the Warsaw Confederation), and capital punishment was extremely rare.^[7] "
5. Some Ashkenazim did follow Sephardi/Biblical practice by naming their children after living relatives. Many, however, did follow Ashkenazi custom of naming children after decedents, including deceased children. This continued among Anusim.
6. Ashkenazim were well aware of the events in Sepharad. In fact, Ashkenazim were also among the first Anusim. "The vituperation heaped on Jews by Christian ecclesiastics, and the violent methods employed by the church in the fourth century (see Jewish *History, Middle Ages), led to many forced conversions. There is clear evidence that anusim existed in the Frankish kingdoms of the sixth century, for the typical pattern of mass violence combined with threat of expulsion is already present in the mass conversion of many Jews to Christianity in *Clermont-Ferrand in 576. The almost inevitable result of the creation of a Jewish "underground" within the Christian society is also clearly visible." (http://www.jewishvirtuallibrary.org/jsource/judaica/ejud_0002_0002_0_01173.html) Also, "In Jewish sources, the term anusim is applied not only to the forced converts themselves, but also to their descendants who clandestinely cherished their Jewish faith, attempting to observe at least vestiges of the *halakhah, and loyalty to their Jewish identity. Both the elements of compulsion and free will enter the psychological motivation of the forced convert. The concept denoted by the term anusim, therefore, is fluid, bordering on that applying to apostates and even to *Marranos; it has been the subject of much discussion."
7. Anusim often hoped that their descendants would someday return to Judaism, especially when (as they believed) Mashiach would come (since they did not generally believe that Yeshua is Mashiach). Many Biblical verses can point to this, and "Anusim and Chuetas keep traditions and have great motivation to return fully and openly to Judaism. Unfortunately, many come across the shock of official Orthodox Rabbinical Halacha as a barrier to their acceptance into Israel. When we open our gates to the Anusim and Chuetas we will see the next great Aliyah, and a massive return to Judaism." (http://israeltheviewfromhere.blogspot.com/2012/10/anusim-maranos-conversos-chuetas-secret.html) Again, this does not apply to just Sephardim Anusim. In fact, one group states their mission as "We are a group of Orthodox Jews (Ashkenaz & Sephard), "Returnees" and converts sensitive to the issues concerning return of B'nei Anusim to their ancestral heritage." () Be aware that this group is extremely Anti Messianic and even Anti B'nei Anusim in some cases--e.g., "As advocates for B'nei Anusim we facilitate Halachic Return and Halachic Conversions, rescue B'nei Anusim misled, or deceived, by Messianic Groups, and lobby for broader recongition of B'nei Anusim in Authoritative Rabbinic Groups." and "This is understood to mean that if parents do not pass down Jewish customs and traditions to their children - then by the 5th generation those descendants are considered non-Jews (even with their Jewish geneology [sic.]). In such a case, Halachic Conversion is required to be accepted back into the Jewish community - this holds true for all Jews, at all times, in all lands - not just B'nei Anusim."
8. Look for inconsistencies in records, names, etc.. In fact, I just found that Regina Jantozonková Czarnogurskyová gave her names as "Antonizonka" and "Jantozonka" (See FamilySearch.org). Also, Andrew Rusnak's granddad borrowed "Kvetkovits" from his neighbors to use as an alias. 
9. Look to see if they kept in contact with their Non-Anusi relatives. Sometimes, they did not because the Non-Anusi relatives were angry at the Anusi ones and sat shiva for them. In the Czernecki and Andrulewicz families, as my granduncle Tony wrote to me (though he had "serious doubts" that we are Anusim, although he basically--albeit unitentionally--gave a clue away), "Periodically a church pastor would run a heritage trip back to Poland for a group.  Very few of those who immigrated would return.  Occasionally someone "in the family" in America would join a relative for the return trip, Usually meeting the Polish or Slovak relatives for the first time and occasionally maintaining a letter writing relationship afterwards.  This DID NOT happen in our family. There was not very much correspondence with the Polish family.  Only an infrequent letter.  There were no exchanges other than through the Polish Church which would have clothing drives and send clothes to Poland in general, but not to specific family members.  Bertha's photos which came after the trips were the only contact until they asked for the deed to be changed in the mid 1960's." As for the famous "Kerry" (Kohn) family, they did (Search for a Rusznak in Budapest, and you will find that "Otto Kerry" is associated with that Rusznak--who, as far as I know, has no direct relation to us [and with "direct" meaning besides that we're related as Jews, anyway].). As for the story re Vilmosz Rusznak and Mary Rusnak Gaydos, let's just say that she betrayed his trust in any Jew who professed to believe in Jesus--one of whom he obviously wrote to as a means of last resort and per piku'ach nefesh. 
10. Think about the Kerrys. They assimilated and pretended to be gentiles. Similarly, the Czerneckis, "settled among Polish, Slavic, Hungarian, Lithuanian, and Ukrainian people just like themselves.  Similar language, similar customs, similar faces, houses, churches, etc.  But life was much better than on the farm.  They were quite happy in America and much better off.  The motherland, Poland, was far off and just a memory, not to be forgotten but no regrets for leaving either." The pogroms, being rejected by family living with, and Anti Semitism in even the United States were not worth dealing with for them--they didn't want the pogroms in Polish Russia, their conversions questioned in the same, or to be called "Christ killers" in the United States (Open Jews in the U.S. did get called epiphets such as "dirty Jew". In fact, in The Color of Water, James McBride relates that his mother recalled a classmate asking her, "'Ruth, when did you become a dirty Jew?'"--and after she took the name "Ruth" to assimilate a little, since that was seen as a more-gentile name--although Ruth the Moabite converted to Judaism, but "Ruth" was seen as more gentile than "Ruchel Dwjoa Szlyska" or "Rachel Deborah Shilsky".).
11. Remember that sometimes only one parent would become an Anusi Yehudi, or both would become Anusim for a time, go back to Judaism, or even perhaps go between Anusi and regular Judaism. Also, keep in mind that children were sometimes considered "illegitimate" when they were "legitimate" but did not have their dads backing their mom's decisions.

I could also gave plenty more clues, I think.