I believe these to be prototype round coins. The earliest spade and knife coins did not have inscriptions, so maybe the earliest round coins may not have had them either. I don’t know by what margin I missed them, but it was at most a few hours. I would say it is my most devastating loss while collecting ancient coins. Unlike the OP coin, I don’t know if there are others extant, and I doubt these will come back on the market.
I didnt see these. What auction did they appear in? I'd like to compare them to what else was being offered.