This coin type is catalogued as Sear Byzantine (SB) 268. Even though it doesn't price as a very rare variety I haven't been able to locate another example in my searches. Note that Sear puts general pricing on coins rather than a scarcity rating. There is also another similar variety in Sear, shown as SB-268B, that simply states is the same as SB-268 but without the christogram. I also was unsuccessful in trying to find an example of this coin online. For the last few years I've been looking for this variation with no luck ... until last week. And here is the 16mm twin: OK ... I guess it is the same as 268 but it appears to be a fraternal, and not identical, twin. I am not sure why the first coin is of much finer quality than the second. Perhaps it was issued for a special event or occasion. In any case it's nice to finally have found my Justinian white whale.