To get a sales letter you first have to be a subscriber to the U. S. Martial Arms Collector magazine. This costs $35 per year (4 issues). Then you have to ask for the letter showing the date of sale, and to whom and the city of residence of the person who bought the gun through the DCM. This costs $65.00. As a collector I consider the value of the sales letter worth what it costs. I have sales letters for all the rifles that I own that are on the SRS list.
The address of Springfield Research Service can be found by an internet search.