My B40WD was first registered in 1982 but, for some reason, only the serial number was recorded on the V5C for the engine and frame numbers - both numbers match but are missing the model designation, namely, B40GB signifying that it was originally issued to the army.
I tried to persuade the DVLA to add B40GB on the front of each number but they insisted on being shown proof that this was how the bike left the factory. In the end I decided to try and do this via a Dating Certificate from the BSAOC.
I sent the letter and Dating Certificate to the DVLA by recorded delivery and noted that it was recorded as having been delivered on 2 Nov. Today, having waited 6 weeks, I phoned the DVLA up to find out what was holding up my amended V5C. They told me the letter and Dating Certificate had not arrived!
Counter to what might have been expected, it was actually the Royal Mail sorting office in Swansea who signed for the letter, presumably on behalf of the DVLA. It then got lost between the sorting office and the DVLA. There's a small chance that they might find the letter from the tracking information but I have decided to start the whole process again with another Dating Certificate from the BSAOC.
The moral of the story is: don't send documents by recorded delivery to the DVLA - it will not confirm that they have got the documents and, by adding an extra step in the delivery process, might actually increase the risk of it getting lost in the post. My approach in future will be to send any documents by 1st class post and then phone them up a few days later to confirm they got it.