I bought a Cota 350 from the US about a year ago, it appears to be quite original other than things like mudguards. I'm about to strip the frame in readiness for sandblasting but am curious what these stickers on the head-stock refer to and are they significant and whether I should try and preserve them. Might be something that only US people can answer?   Pics attached. 

My money is on the blue and red stickers being road rego stickers from 1987

Here in the US many states have stickers for off road use.  It's a lot like road use stickers... however with road stickers they go on a road number plate instead of the fork tube or head stock like the off road ones do.  

The number on the side is a serial number and is for bike identification in the case of theft and recorded during registration for street or off road stickers.

Edited September 9, 20178 yr by jonnyc21

Thanks Gents, makes sense. I did realise that the 51M on the side was my frame number, I didn't really need to add that pic in hind sight.