My cross reference doesn't show any 04M-495B by Western Field.
Western Field was a brand name used by Montgomery Wards and many of their guns were actually made by Mossberg.
Of the guns I did find with the 04M prefix, all were Mossberg's, but appear to be shotguns.
Without a positive ID of exactly which company actually made your gun, and the model number, there's no way to know a production era.
You might contact Gun Parts Corporation and ask them to ID it for you.
They're the prime parts supplier for these older guns, and they should be able to ID it for you.