This appears to follow the Monarch in reverting to wire staple guides in early 1942. The WW2 wire guides are steel instead of brass. If the LS follows the Monarch in other things then the brass sheet staple guides started in 1910 and the single MAY-4-20 patent in 1934. This is the original fill cap if it has brass threads to match the brass fill port. I believe that all Dietz hot blasts after 1897 were made in Syracuse where cold blast and other random patents were commonly stamped into them.