Don't know exactly how old this would be, but it certainly looks better than what the NMRA came up with. GS
My brain is foggy, but for some reason, Baker or DeVore comes to mind. I think I even have one of these in my junk box.
I thought Baker was a loop n' hook type coupler. I also think John Allen preferred Baker couplers? I've seen examples of the coupler in question, but unfortunately, I haven't a clue as to who manufactured it.
Is this diagram a fair representation of a Baker coupler? I remember these from nearly 70 years ago. On topic: Could the unknown be a Varney coupler?
"Found from some Web surfing" June 1949 MR - first ad for the "Devore" coupler. January 1952 MR - last ad for the coupler under the Devore name. Same issue, MDC ad showing the couplers on a box car. So it appears the couplers were only sold under the Devore name for about 18 months. April 1952 MR - MDC with multiple rolling stock pictured, all have the couplers and ad says "with automatic couplers". July 1952 MR - MDC ad says all kits include Model Die Casting's "famous automatic coupler". That was a pretty quick evolution from a product that was brand new in 1949 and by 1952 is the "MDC famous automatic coupler".
Last night I found that same MDC package in another bunch of old stuff from the same guy. They actually are more scale sized and look a little better than the original Kadee K-5, but being rougher die castings they probably didn’t work very smoothly.
I just went through a 1952 issue of Model Railroader magazine and looked up the list of Advertiser's. MDC Model Die Casting was listed and it showed one of its product was a Roundhouse EJ&E "Belt Line" box car kit factory painted & lettered, flexible coil spring trucks, draft gear automatic couplers for $2.70. Also, on the same page, Roundhouse manufactured model paint in 48 cc size for $.40 Talk about being born too late!
In 1952, $2.70 was a fairly high price for an HO scale boxcar. I remember buying Athearn cars in the early 1960s for about two bucks. GS