When using coins in trade-o-mat to buy resources from other players, trade-o-mat merges coins into higher possible, effectively limiting amount of trades that can be done to 8 without owner manually changing coins back to smaller nominals. Trade-o-mat is then unable to split coins to continue trading.

putting enough coins for 320 trades:

doing one trade:

doing 7 more trades, now no more trades are possible:

Back in personal storage, we see coins has merged:

Only 1.19.2 since i rewrote the entire system in each version and they work completely different in each