So thanks to @pelrun tonight we’ve deciphered the output from these readers in a meaningful way.
The hex string the reader outputs is just the hex conversion of the decimal card ID. Without the RS232 converter inline the hex bytes we were recieving were wrong and so we discounted that possibility at the time.
Basically I forgot to check that option after adding the rs232 converter breakouts online because I was too busy focusing on a few aliexpress pages with the same model of RFID reader that had stated the format was ABA TK2.