I found this on the weatherby website, I guess I should have checked there first:
Over/Under Shotguns Series # Pre-fix
Regency® (Italy) Over/Under (1967 – 1982) R
Olympian® (Japan) Over/Under (1977 – 1981) K-R-W
Athena® (Japan) Over/Under (Version I) (1982 – 1990) D-F-FF
Athena® III, IV, V (Japan) Over/Under (1990 – 2007) DA-DF
Orion® (Japan) Over/Under (Version I) (1982 – 1990) E-G-EE-GG
Orion® I II III (Japan) Over/Under (1990 – 2007) EN-ER-GN-GR
Side-by-Sides
Athena® SxS (Italy) (2005 - ) FS
Orion® SxS (Italy) (2005 - ) FS
Athena® D’Italia III, IV, V (Italy) Over/Under (2007 - ) L
Orion ® D’Italia I, II, III, SC. (Italy) Over/Under (2007 - ) B - L
So according to this, his orion is the 1982-1990 version (serial number prefix is E)...so I guess it doesn't have a grade.