|Virginia Halfpenny N20-X. Image from StacksBowers.|
The notion that coins or tokens were used as communion tokens is not so far-fetched. The round Port Glasgow tokens (BZ5774 / KL(40)244) appear to be stamped over a (yet-unidentified) token. There are probably others too -- let me know if you know of any. Certainly, the use of a countermark was practical. I am surprised that it did not occur more often. Or, maybe it did, and we just do not know about it. However, to my knowledge there is no documentary evidence to support the notion that coins and tokens were counterstamped by the Presbyterian Church.
Image from StacksBowers.
Here is another piece that could be a communion token. This time a Massachusetts Cent provided the host coin. The deeply impressed countermark -- PC -- could stand for Presbyterian Church. Again, we have no documentation. Bason only lists two CTs with these letters -- only one of them signifying Presbyterian Church (the other CT is from Peters Creek, PA).
Still, we know that early USA CTs were quite primitive, as most everyone was busy carving out a life in the frontier. It would not be a surprise to learn that counterstamped coins and tokens were used as communion tokens.