Here's a Ref 1002. No date Oyster Perpetual chronometer, 34mm case:
Here's a Ref 1018. Same specs,except 36mm case.
Both were made throughout the sixties. The 34mm was made until 1987ish. The 36mm seems to have been stopped earlier (stepping on the Explorer's toes?) When I came to write this I thought they were stopped c.1970, but I've just seen an advert for one made in 1978.
Does anyone know when they stopped making the 1018?
I'll be continuing to google