Buck was granted a patent on the 'American'  model in 1972, transferring the right to produce that patented guitar to the Chicago Musical Instruments company. It took a while to get the design patent, as Buck had applied for it in February of 1971. By the time his patent was granted in November of 1972, the 'American' was nowhere to be seen in the Sears catalog.

That's all I know for sure.

The stamping inside the models we see is certainly Harmony stamping, and the guitar itself is very similar to the H180/181 models of the time. The stamped designation in every example I've seen has been H169 following the serial number.