Here is a blast from the past – the 1991-vintage Electro Prismatic Collimator (EPC) Sub-Miniature Red Dot Sight from Ring Sights.

The EPC was based upon Right Sights’ basic solid-glass LC-7 optic, the forerunner of the LC-14 used on the FN P90. The EPC’s Planar Doublet Reflector (PDR) was made 8 mm square with a dichroic beamsplitter reflecting red to give better night vision capability. The red dot was lit by a LED powered by two NR48 hearing aid cells in a housing molded into the side of the optic housing. Dot brightness was automatically controlled by a photo-diode to match the ambient lighting. The battery cap also served as the on-off switch. It could be switched on and off manually or be assembled in “combat mode”, which left the sight permanently on until the switch was removed. Ring Sights would later admit that the switch mechanism was troublesome and the cause of many returns.

The housing used a curved base to allow movement for zeroing. However, zeroing was only possible while the sight was being mounted…via epoxy! A two-part aerospace epoxy was used to glue the sight into place on the slide.

Ring Sights claimed to have sold over 100,000 units. Most were for pistols, but there were also some used on sub-machine guns, most notably by the Channel Tunnel police. The EPC was reportedly usable with night vision goggles, and Ring Sights claimed that an untrained person could hit a man out to one hundred meters at night.