Where does it say that Vince....... It must be my age. But if it is a double dovetail, there is a simple explanation. If a gun body had a fault during manufacture that after consideration, could be rectified instead of being scrapped, it could be diverted in a couple of directions. If it was already serially numbered and therefore accountable (for security and contractual royalties purposes) it might go to the training department for apprentices to section as a training aid. Or it could go to a 'rectification' bay - commonly known as 'the hospital' where skilled machinists could put the mistake right and save valuable time and money.

So it is quite feasible for a D/D Mk1 gun to be diverted to the hospital and come out much later and be allocated a later serial number prefix, such as this one(?) Depending on the outcome of the rectification, some of these guns bear the letter A following the serial number.

One Mk1/Mk1-A intermediate gun has a ‘K’ serial number prefix when its features tell us it SHOULD have a ‘E’ prefix. Others such as E-906A and H-7070A that had clearly been rectified and were over engraved with the A suffix