I dont see how mint A would ever know anything about mint B. What do you mran by validate a token? What makes it valid? The way ecash works is your wallet holds the tokens. When they are recieved, it redeems them from the originating mint by asking for new tokens of the same amount. The only way two mints are associated are through lightning. You can ask a mint to pay a lightning invoice with your tokens from that mint. The invoice could be from a lightning wallet or from a mint, but in either case the mint sending sats over lightning doesent know what the sats will be used for. No two mints accept tokens from each other.