Callu, who pointed out the Hispanian liking for late AE2s, was certain that it they were imported by
choice. Of course it was
still likely due to trade but it is interesting that one
area (
Hispania) got many AE2s while southern
Gaul and
Italy did not (they only
had the AE4s by then).
I don't think that
Spain was such an important source of metal by the late
Roman era but I might be wrong.
You can
search and find several
good forvm threads dedicated to the
XXI mark.
The brief summary is that it was thought for a long while to be a value mark - 20
sestertii and therefore 5 denari communes. However, that argument is disproved by the existence of a few short lived issues with XI on them. If it were a value mark then they should be half value yet they actually have twice the silver content of the
XXI and thus are worth twice intrinsically.
There are two remaining views of the
XXI. One is that it means "20 for 1" and the other that it means "20 and 1".
In the "20 for 1" theory it means it is worth one 20th of a silver coin. The problem is there was no silver coin issued during this period (274 - 294). Two theories have been put forward in response. One is that it was for a silver coin that was intended by
Aurelian but never introduced. The second is that it referred to silver
denarii of the 2nd and early 3rd century which were
still in circulation and
still legal tender. The mark is thus one of value but by ratio and not by absolute value.
In the "20 and 1" theory it means that the coin is made up of 20 parts bronze and one
part silver. The mark is thus a guarantee of purity. The assays of the coins from
Aurelian through
Probus appear to match this quite well though it
fineness level falls a
bit under
Carus and
Diocletian.
The XI coins
work in either system. Given their doubled silver content they are either worth 1/10th of a silver coin or have 10 parts bronze to one
part silver.
I personally favour the latter argument.
Shawn