Nice find Wats6831. It's not my impression that an HBM scope from the 3000 range is that unusual. I had several in the past, including one numbered 3057, which was a bit unique in that it was dated 1941 in the engraved markings. That was apparently dropped for "security" reasons shortly after.

The reason there are so many MkI scopes around is that there was a post-war refurbishment program that replaced perhaps most of them with later types. I was told by a now deceased surplus dealer in the UKicon who specialized in optics in a very big way, that his firm had bought about 5000 MkI scopes from the MoD during the 1950s and used to sell them for £5.00 each in the case with the mounts. Mind you, £5 was about an average week's wage in 1950 and it hadn't changed much by 1960 from what I've read!