Hi all, I noticed a difference in the copies I have of Archer manuals: in the 1946 handbook there is a reference to a No 51 LC telescope (LC?) and in a 1952 RAC handbook it's a No 43. I gather from elsewhere: No 41: used in towed 17-pounder guns No 43: used in 17-pounder armed tanks and possibly the M10C No 51: I have no details other than x3 magnification - although what is written in the book says "Type No 51 LC (illuminated and graticuled)" so perhaps LC refers to lighting? I'm not sure. I'm wondering if, like the radio model numbers (e.g. both No 18 and 38 were man-portable sets), "51" indicates that it was a development of the "41"? Does anyone know more? By 1952 a later version of the No 43 seems to be employed, as this No 43 has a replaceable eyepiece so the gunner can choose between 3x and 6x magnification.