The outside diameter of the No32 tube is an easy one to remember. Exactly 1"
Interesting question as to why the number has been obliterated. I never understand why one would obliterate a serial number because it's just a sure-fire way of saying that I have got some stolen property! And anyone stealing a telescope 'in service' would really be taking a HUGE chance because the telescope, being serially numbered to the rifle AND of itself AND being a what we call WOCS (War Office Controlled Stores) item is highly controlled and all that goes with it. Loose one and the proverbial would hit the fan before you could.......... anyway! Then there would follow a what we call a Board of Enquiry as the start of the Army judicial process. To learn about that, something that I experienced at first hand, read the article about the Centurion Tank titled 'Revenge, extracted in full'
But, that being said, we did have a scope and bracket appear in our Armourers shop one day, found on the 600 yard firing point, presumably left by the snipers the day or week before. Only some judicious book cooking can cover a loss like that and if the long serving Quartermaster would cook the books to cover such a loss, then......... Anyway, I never came across one!