Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Yep, nothing unusual. The individual code letter, in this case 'E', would be issued to another airframe in the event one was lost, transferred to another squadron, or non-operational for whatever reason. As an example, it was not uncommon for an aircraft to be on a squadron as, say, 'E', and then be moved to an MU for repair, modification or whatever, only to return to the same squadron, and then be marked as, for example, 'G'.
This shows up often in research, where an aircraft is found on squadron records wearing two, or even three, different code letters.
Missing from a mission to Aachen, 24/25-5-44.....