Normally we expect to see Constantine's mints all pretty well synchronized, so it's always interesting when some mint does something different.
When Crispus was executed c.326 AD, his step brother Constantine II, next in seniority, was handed control of Crispus' prior gallic territory, and Arlelate was renamed Constantina in his honor. We see this reflected in the Arelate mintmarks which change from PARL to PCONST.
Aside from the renaming of Arelate, Constantine II's moving up in the pecking order is barely reflected on the bronze coinage (not sure about the gold - would be interesting to look). No doubt Crispus death was a rather shameful affair, and the less attention brought to it the better.
One interesting exception to this is at Nicomedia where we see a tiny reflection of the change. While Crispus has been alive Nicomedia had used "LDC left" busts for all 3 caesars, but after his death they switched to an LDC (right, not left) bust for Constantine II, apparently as recognition of his elevated seniority. What's interesting is that this change appears to have happened immediately, in the middle of the "MNA" issue mark.
It seems coining in the MNA mark (when the campgate reverse was in effect) can be divided into three phases:
1) Initially the reverse legend for the caesars is PROVIDENTIAE CAESS and coins of Crispus and Constantine II appear equally common, and fairly abundant.
2) The mint inexplicably changes to a PROVIDENTIAE CAES. legend, while continuing to coin for Crispus. Whatever the reason for this legend change (aesthetics - more symmetrical break?) it would therefore appear unrelated to Crispus. During this phase Constantine II still has an LDC left bust. Coins of Crispus and C2 are both R4 - evidentially this phase did not last long.
3) The mint switches to the new LDC bust for C2, with these coins being R1, apparently having dropped Crispus at the same time.
The corrdination of this unexpected mid-issue bust change for C2 with the dropping of Crispus (RIP) can best be seen by the relative rarity of the coins. If Nicomedia had instead continued to coin for Crispus until end of the MNA "issue" mark then we'd expect continued similar abundance for CR & C2 until the end, rather than only up until the bust change.
So, perhaps only a minor point of interest, but always interesting to see one mint acting alone.