Help Fine Tuning An ID?

That's a really cool looking coin. Nice.

It's not a bad looking coin, but I did use electrolysis on it. Note: I looked at the huge variety of reverses on Gallienus coins at Wildwinds. Someone could make a fun collection collecting Gallienus reverses!

I think that what letter the arrow points to is incidental, just an outcome of the particular die engraver's layout. It doesn't affect the citation/reference.

RIC's approach varies from volume to volume, which were written by different authors. It can be frustrating. Several different bust types and mint marks may be subsumed under a single number. In other places, coins with identical descriptions are attributed to two or more mints, listed separately, and can only be distinguished subjectively by style. In the late period, the same coin may be given two numbers because of a change in the imperial college during it's issue. That being said, RIC is what it is and though some volumes are now nearly 100 years old, it remains the standard reference. The Romans struck enormous numbers of coins, employing many dies for each issue. RIC lists more than 1100 numbered types for Gallienus alone, comprising thousands of listed varieties. I couldn't begin to estimate how many dies that number implies.