When did Weatherby produce rifle scopes?

Mark XXI ® scopes Manufacturer: Asia optical (Japan) 1964-1989
Sightmaster® spotting scope Manufacturer:  Asia optical (Japan) 20X-45X: 1972- 1982 20x-60x: 1983-1989
Imperial® scopes Manufacturer: Hertel & Reuss,  (West Germany) 1954-1973
Premier® scopes Manufacturer: Asia Optical (Japan) 1973-1982
Supreme scopes Manufacturer: Asia Optical (Japan) 1983-1994