About 40 years ago I had a BSA 4x20 and being an inquisitive teenager I had to pull it apart. I thought I would put my little finger down the tube which met a little resistance, and then a little click which was me putting my fingers through the cross hairs.
I got the bus to Manchester Air Guns and bought an
ASI 4X40wa (and a set of mounts + an arrestor block in a red and black plastic box) which I was chuffed to bits with.
On my way home on the bus I opened the box up to look at my purchase when a lad behind me said "Wow, that looks like something off a sniper rifle".
I'd forgotten about that until you started this thread Paul.