I was at a military surplus place this afternoon, and came across five 'L2A1 Sight Periscopic A.V. Image Intensifiers'. These were night vision devices the like of which I've never seen before. They were about five feet long, had binocular eyepieces at one end, and the mother of all objective lenses at the other. They made 'TWIGGY' systems look tiny in comparison! In spite of the 'periscopic' bit on the nameplate, they didn't actually seem to be periscope-type systems - rather, they looked like huge spotting scopes. They did, however, have very precise-looking adjustment wheels on the side, so my guess is that they're some kind of weapon sight. I was wondering if anyone here can tell me anything about them? Such things as what kind of mechanism they use (Cascade/Gen II, etc.), what they were used for, and if they're any good. The only thing I can think of using one for is as a donor to build a giant wildlife NV camera, but then again, I'm into that sort of thing. As ever, any help would be most appreciated!