I remembered James Earl Ray and his rifle the moment I read "Aeromarine" on your letter. A somewhat unusual name for sporting goods.......Here's a bit more on them:
The Aeromarine Supply Company (originally Aero Service & Supply Co.) was a sporting goods retailer. It began as an automotive and aviation supply company founded by Harold Wood, who also owned the Wood Chevrolet dealership. His son, Robert took over management of the business after World War II and changed the name to Aeromarine in 1955 when he took ownership of the company.
The original store was located at 5701 Airport Highway in Woodlawn. James Earl Ray purchased a Remington hunting rifle at that location on March 30, 1968. He later used that gun to kill Martin Luther King Jr in Memphis, Tennessee.
Yes, this frame was one that sat on the shelf for several years. The O.S. means "Old Style" which signified the early frame. There is quit a gap in serial numbers between the two that were shipped just two years apart.Cam, I find it interesting the square butt shows a 1921 serial number and narrow square butt grip frame (basically eliminated from production by the end of 1927), yet wasn't assembled and shipped until approximately 13 years later in 1934.
As we all know, manufacturers never threw away parts that were superseded unless they were deemed unsafe. However, the gap between this serial number older narrow square butt PPS frame and the date the revolver was shipped seems even more out of a normal transition period to newer parts
Do you know what an "O.S. Frame" is?
"Old Stock Frame", perhaps?