Very interesting…..you don’t have a list of prefixes do you?

There is, but I wouldn`t know where to start looking for it. If it turns up I will post it on here.
A, F, G and K are another 3 which crop up quite often, and, of course GN, which are Griffon parts subsequently fitted to the Merlin.
There are also quite a few dual prefixes, most common is KB which often applies to studs, I seem to recall that this is not from an earlier engine, but I can`t be sure about that.
Tooling is often prefixed HB (I wondered if this stood for Harvey Bailey), but again there are tools with D and E prefixes, so there was no particular logic. Packard tools are prefixed AT.