Another article focusing on Simon ben Kosiba.
The article claims the following writing by Justin (First Apology 31.6) is in reference to Simon ben Kosiba.
For in the Jewish war which lately raged, Barchochebas, the leader of the revolt of the Jews, gave orders that Christians alone should be led to cruel punishments, unless they would deny Jesus Christ and utter blasphemy
The star above the facade of the jewish temple in the coin may or may not have messianic connotations.
Letters attributed to Bar Kosiba's administration may also be of interest (see abstract below).
Two letters from Nahal Hever, one in Greek and one in Aramaic, deal with the requisitioning of the "four species" (palms, citrons, myrtles and willows) for use in the festival of Sukkot (Tabernacles) in the camp of Bar Kosiba's army. The first part of the paper presents the two texts with critical comments. Following the lead of Yadin and others, I argue against the identification of the sender of the Greek letter, Soumaios, with Bar Kosiba himself. In addition, I propose or defend readings that differ from those of the editio princeps and subsequent publications. The second part of the paper draws attention to a number of issues raised by the two letters taken together. The letters offer an interesting window into the chain of command and delegation of authority in Bar Kosiba's administration. Because one of the letters is in Greek and includes an apology for the fact, the letters testify to both the extent and limitations of bilingualism among Bar Kosiba's supporters. If Soumaios, the author of the Greek letter, was a gentile, gentile participation in the revolt requires comment. Finally, I consider the implications of the festival of Tabernacles for our understanding of the second revolt, drawing attention to associations of the festival with both Temple rededication and eschatology, Sukkot and Temple imagery on the coins of the revolt, the use of branches in the representation of royal figures and of victory in classical literature, in the royal propaganda of Hellenistic and Roman rulers, in the New Testament and in ancient Jewish literature, and, most immediately, on the coins celebrating the visit of Hadrian in Judea in 129—30.
LAPIN, HAYIM. “Palm Fronds and Citrons: Notes on Two Letters from Bar Kosiba's Administration.” Hebrew Union College Annual, vol. 64, 1993, pp. 111–135. JSTOR, www.jstor.org/stable/23508440