i bought it off ebay for a very reasonable £70 i had a large sidewheel made for it as they dont make them for the bsa. mine was just 10mm thick aluminium lazer cut. mine has an internal dia of 37mm and and external of 157mm. this is the largest i could design which did not hamper the zoom ring. as i said the scope is reasonable for the cash. i dont use it for serious comps but it got me started, it was repeatable in the sense of rangefinding. the only real problem is use in a very dark area. the objective lens is only 44mm dia.
but overall worth a look.