Found some info for Big bores
some links for those interested in reading some posts
Scroll down an scan some posts for more info
http://www.shootersforum.com/leverguns-their-cartridges-general/20221-big-bore-serial-numbers.html
seems my BB046### is around 1981
Winchester Big Bores (MC=Monte Carlo Low=Low profile stock)
S/N Stock Caliber Action Safety
BB001### low .375 Top No
BB004### low .375 Top No
BB0090XX 375 top made in 1979
BB011### low .375 Top No
BB016### low .375 Top No
BB020### low .375 Top No
BB035### low .375 Top No
BB035### low .375 Top No
BB036### ? .375 Top No 1981? XTR
BB037### low .375 Top No
BB040### low .375 Top No
BB041### low .375 Top No
BB043### low .375 Top No
BB044### low .375 Top No
BB0445XX 375 top made in 1980
BB045### low .375 Top No
BB051231 ? .375 ? ?
AE11### MC .307 Angle No RockIslandAuction
AE12### MC .356 Angle No RockIslandAuction
AE125XX 307 MC made in 1984
AE135XX MC .356 Angle No
AE16### MC .375 Angle No RockIslandAuction
AE16### MC .375 Angle No Not drilled for scope
mount-transition gun?
AE160xx MC .307 Angle No
AE18### MC .307 Angle No
AE19### MC .307 Angle No
AE230xx MC 375 Angle No made 1985 Mark Twain Commemorative
5588### low .307 Angle No
5624###low .356 Angle No
6029### low .356 Angle Yes ( bought new around Mar. 1992)
605###x low .356 Angle Yes
6214### low .356 Angle Yes
6279###A low .356 Angle Yes