"NMRA" couplers is the generic name given to the X2F coupler design that the NMRA promoted starting in the '50s. It is that big hook type coupler with the rigid pin sticking down and is pivoted at the pocket. They are most easily recognized by the large wing on the coupler head to one side. Their first problem is that they force the car to one side when coupled to another car. Most manufacturers used them until the Kadee clone couplers came along. Lots of people problably have drawers of them (if they bothered to save them!) floating about. I'll also note that each manufacturer had different standards for the coupler, especailly in the pocket area.
-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!