As a "Rule of Thumb" it is thought that the 'Alloy' guards were installed as "standard" after WWII when the factory moved to Chicopee Falls,Mass. However, I have seen pictures of one M220 that the owner says his father purchased in 1937, which would be a very early gun, and it came with an alloy guard. I have not observed any guns made starting in 1947 when the factory moved to Chicopee Falls, Mass., with steel guards. But.....if a steel guard was bent badly, it could have been changed out with an alloy guard after the plant moved. I have not been able to determine when the Utica guns began using the alloy guards. For ease of identifying, I call the Utica guns with the steel guard and slim trigger a "First Model Utica". Utica guns with an alloy guard and slim trigger I call a "Second Model Utica" I have found M220's with Utica barrels that have color case hardened frames, which did not start until Chicopee Falls. Most likely these were parts already made and marked Utica and moved to the new plant. The more I research these guns, the more "variables" I find. I hope this helps. Happy New Year!
