I've bought two interesting Gallienus antoniniani some days ago.
1) 4,50 gr (very heavy) and with a letter in the left field (a "V"?) and, if you see with attention, a star on the right field. The style is not so good and also the flan is not so regular
2) 2,9 gr (regular size), very good style and "V *" in the field like PAX of Victorinus...
I don't remember for Gallienus this cuple of mint mark... I remember "V" and "*" but not together... may be a couple of barbarous radiates? or they are both official coins?
Sorry for my english.