Ray of sunshine posted:Roy,
Kadee couplers came out sometime in the mid 1950's. But NMRA was still the standard. By the early 1960's, most HO scale modelers, including myself, started converting to Kadee couplers. By mid to late 1970's, many manufacturers started to include Kadee and I would guess by late '70's the NMRA coupler was a dinosaur. Kadee was the norm from all major manufacturers by then.
Ray
I recall the NMRA X2f coupler was actually developed in the late 1950's. Prior to the X2f's most HOer's used either the Mantua loop couplers or Baker couplers. There was also a functioning scale sized knuckle coupler from Model Die Casting. There were also various dummy couplers availble.
The X2f was a solution for an inexpensive coupler made available to all the manufacturers for standardization. Reliability left something to be desired, but it still became the standard HO coupler for decades..
The Kadee patents expired in 1997, allowing the various Kadee clones to be offered on HO products.
Rusty
