The question is "Just who are those today who claim to be Jews (of Judah) but are NOT?"
The following are a few short excerpts taken from the subject titled "Khazars" in the " Encyclopedia Britannica", 1973, pgs. 328-330.
Most people have never heard of the Khazars or their empire which at one point "exacted tribute" from 23 nations. Of course the "seed of the serpent" has been marked with "cover-ups" ever since the fig leaves were sewn together in the garden of Eden. Hence the last two sentences of the Britannica article should come as no surprise:KHAZARS
"... Khazar civilization shows a fairly complex texture and their religious life raises more than one problem. Christianity, Islam, Judaism and some sort of "pagan" worship are all attested by sources. About 740 the Khazar ruler - and probably the greater part of the ruling classes - were converted to Judaism. The circumstances of their conversion remain obscure, the depth of the Jewish layer difficult to assess; the fact itself is, however, undisputed and unparalleled in the history of central Eurasia.
"The story of this conversion of the Khazars had a considerable and lasting impact on the western world. The first to record it was Druthmar of Aquitaine (9th century), but circumstances of the conversion are related in greater detail in various Hebrew documents such as the so-called "Khazar Correspondence." This consists in a letter (c. 955) from the Spanish Jew Hasdai ibn Shaprut to the Khazar king and in a reply (of contested authenticity) sent by Joseph, king of the Khazars.
to light the remains of the Khazar fortress Sarkel,
on the lower Don, built in the 9th century with the help of Greek architects.
This site, which clearly revealed the mixed character of Khazar civilization,
had to be inundated during the construction of the Volga-Don canal."
It is obvious the the people we refer to as Jews today are even less representative of the Israelite tribe of Judah, today then they were when Jesus said to the Jews in John 8:44 "Ye are of your father the devil, and the lusts of your father ye will do". Read John (Live Link to- chapter 8 in its entirety, especially vv. 22-59 and tell me again what Jesus meant in Rev. 2:9 and 3:9.