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What company built Western Field lever action rifles?
To the best of my knowledge Montgomery wards commissioned the rifles through other companies I own A model 895 22 caliber lever action And it is a commissioned Moseberg 402
Probably one available from Numrich Arms (e_gunparts.com), but you should probably let your local gunsmith replace it, so you might as well order it from him.
Western Field was a trade name used by Montgomery Ward for sporting goods made by many different companies. A quick look at the cross-over list shows guns by Mossberg, Noble, Stevens, Savage,...