That's an interesting assembly of coins, and commentary.
So, if there were any rules/traditions, it seems it has to be broader than a rocky
shore. My second guess would be perhaps that the
rocks might represent "
terra firma", or a general allusion to the land, as would be appropriate to one of these
provincial personifications. If that was the general idea, then it's
still not obvious what was intended by a
river god leaning on
rocks - was this essentially the same, or more literally meant to depict the rocky river bed/bank?
In any case, the figure on the
medallion certainly seems to be sitting on something, ankles crossed. The whole scene seems quite unusual and specific, and it's hard to imagine it was expected to be interpreted without any external reference. I assume it is depicting some well known statue, or possibly ceremony, from the city of
Rome. Presumably there is some connection between the scene and the "Secvritas Romae"
legend, although no guarantee.
I'm not even sure how much a better specimen of the
medallion would
help... It might make it a
bit clearer what is being depicted, but I think we'd
still be missing the cultural reference.
I'm sorry for posting in English, but I don't know Polish, and don't trust
Google translate unless it is very simple.