If this was imported by SARCO since 1968(likely) they would have had to keep basic records permanently since this is a BATF requirement. They have imported a lot of surplus Spanish military pistols in recent years so shotguns would not surprise me at all. You may want to contact them; they are now located in Pennsylvania, and see what information the can or will provide.
N.B: They also imported a slew of inexpensive doubles from the Scandinavian Countries around 5 years ago so this was something they probably did in earlier times as well.
Jim
