That is a really nice example, and one I haven’t seen before! Thanks for posting!
Yes, quite
rare. I have been hunting these
Crispus from
Constantinople for some 30 years, and I attach an image of what I have found. Many of these are in museums. Less than one new example
per year turns up.
I just published a paper on the
Crispus coins from
Constantinople. Based on statistical analyses (
Warren Esty was the wizard doing these), we can see that the production for
Crispus was cut short when the news of
his demise reached
Constantinople. The paper:
Aborted Production and Selective Coin Withdrawal: a Die Study of the AE Coinage of
Constantinopolis in AD 326. (2020: Lars Ramskold, The
Numismatic Chronicle 180, pp. 207-257)
Some details can be updated. In all probability, the
mint of
Constantinople opened for
Constantine’s visit in March 326, when he set out for is vicennial journey to
Rome.
Crispus fell from grace just after
Constantine’s arrival in
Rome 18 July 326. I published this in a paper in 2013. For anyone interested, the paper can be found in full on Academia.edu and on ResearchGate.
Constantine’s
Vicennalia and the Death of
Crispus. (2013: Lars Ramskold. Niš &
Byzantium XI, pp. 409-456)