Lyman introduced the No. 66 Series Receiver Peep Sight circa 1955 as a micrometer click receiver sight for rifles with flat sided receivers and it featured quarter minute windage and elevation adjustments, a push button quick release slide assembly, 0.550" diameter eye cup and options of stay set or knurled target knobs. The steel mounting base was changed to aluminum alloy circa 1974. This sight was offered for a wide variety of commercial rifles by Browning, JC Higgins,Marlin, Mossberg, Remington, Ruger and Winchester as well as the foreign military type British Lee-Enfield Mark 4 and 5 rifles. Manufacturing of this model continues even today with 60 years of production thus far.