While learning about optics I came across the Panoramic Telescope gun sight. The thing that's very interesting is that it contains everything needed in a submarine periscope (Wiki). Panoramic means that the telescope can be panned in azimuth. But in a simple optical system when that's done the image will rotate. But in a military panoramic telescope the image stays upright. This requires a sophisticated optical system (see the Kollmorgen Periscope patent on my optics page).
"Telescope, Panoramic M12 A3, No. 12981 F.J.A., E.K. Co. 1943" is stamped at the top of the periscope tube.
At the bottom center of the reticle is "3 IN M62".
TM 9-2005 Vol 3 Ordinance Material - General, Vol 3, Infantry and Cavalry - Accompaning Weapons - Field Artillary, 2nd Ed, Dec 1942
Has a sentenance for "Sighting Devices" where a number of them are a panoramic telescope (most are the M12).
Lists a number of guns and howitzers that use the M12 panoramic telescope. Note that a 3 Inch gun and a 75mm Gun are the same thing. The manual lists five 75mm (or 3") guns, but none of them use the M12 panoramic telescope. A number of the Guns, 155mm: M1917, M1918M1, M1, M1A1 and the 8" Howitzer M1 use the M12 sight.
Looking for TMs that cover the M12 panoramic telescope. Let me know.
Unit History -The 1/92nd Field Artillery Association - Vietnam - M1A1 Cannon Technical Data, Specs -