I am looking for someone who was not where I'd expect at the time of the population register in 1939: John Rhosydd Williams. I have found a possible entry for him in Denbigh, with letter code ZJDE and in the final column the code PWC598/9864. The man I am looking for was a grocer, but became a minister of religion in 1924. The man listed as John R. Williams in Denbigh was a grocer's ledger clerk. They were both born in 1885. Can anyone, please, interpret the two codes to help me confirm or discard this possible identification?
The codes aren't going to help you - one's a location and IIRC the PWC is some kind of War Bond.
The information that can confirm it is the Date of Birth so get his Birth Certificate if it's important to match the entries.