100 Sqn Lancaster WW2 Code letters

Thanks for the replies.
Antoni – what is the source of your dates?

ED583 was used to illustrate the fact that it is shown in 2 photographs with the codes JA-U (Lancaster Operations; I Reid); it crashed on 4 Oct 43, coded HW-K ; (Lancaster627.shaunmcguire).
That is BEFORE the quoted dates of use in Combat Codes of c44/45! The conclusion therefore being that JA codes were in use before October 1943.

Reid, quotes the ORB as JA codes being in use from formation (Dec 42 at Waltham – Jefford, RAF Squadsrons) until MAY 1943 when HW was introduced.

The ORB is usually the best source document and I would lean towards it being correct, however, I have not seen it.

I am attempting to sort out the conflict between sources – both of whom I know are solid researchers.

Could any future replies please quote your sources.