On Monday, July 31, 2017 at 2:09:22 PM UTC-5, wrote:
I am looking for non Internet history, photos, stories and anecdotes about the factory Schweizer 1-20, NX91840, between the years 1964-1994.

Any info would be appreciated.

Guy Byars

The FAA Registry lists the glider under N91840, i.e. without the 'x'.