Essentially a link and pin coupler with a few changes to keep human hands away from the link and the coupler pocket.
Mr. Sams and his manufacturer claimed that the coupler was automatic as required by Federal Law. However, much of the railroad industry did not accept this design -- it had already decided that "vertical plane" or MCB or "Jenney" coupler was their choice. MCB = Master Car Builders, a trade association.
As I recall reading that in1899(?) the standard gauge Rio Grande Western was still ordering freight cars with Sams couplers -- this was at the same general time that the Union Pacific had given notice that it would no longer accept cars with Sams couplers in interchange. These reports from a Salt Lake City newspaper.
The assumption looking back from today is that the Sams coupler was used and survived as long as it did because it was cheaper to purchase that any version of the MCB style coupler.
Brian