s1

This is a very complex story in itself. Suffice to say here, that the Swedish company was named Svenska Aero and the product (eminating from Caspar) used the Roman digit I. Svenska Aero S.I Stig

Designed by Allan & Malcolm Loughead w/ help from Jack Northrop (w/ a rather obvious appreciation for the Albatros design) in 1920, the S-1 (for "Sport-1") was a post-war civilian design assembled in Santa Barbara, CA to be a simple, low-cost aircraft using Loughead's existing production experience. However, the preponderance of cheap, leftover Great War a/c made it superfluous. Features of the S-1 were used in the later famous Lockheed Vega designs. The Scottish "Loughead" name was later officially changed to Lockheed, and the rest is history...