It appears that these last issues (including AE) have a greater variety than most of those of previous years and this, in his opinion, could be linked to Domitian's 15th anniversary.
I am skeptical of this idea, since there was no observable quinquennalian issue of coins for
Domitian in 86 and no decennalian issue in 91.
It's always best to follow Eckhel's principle I think: if we have no apt and probable explanation for a phenomenon, then we should frankly admit that the causes are unknown. It is astonishing,
Eckhel continues, how much light
Roman coins can
cast on a great many matters; so we should not find it disgraceful to admit that some other questions apparently cannot be answered.