I am still looking for information about the M-1 drum conversion, here is what I have learned so far; The drum is an original Bridgeport, mechanically sound with no damage beyond the scope of the purposeful modifications. There is no rust inside or out, to include the internal components. Rounds move freely though the entire path of the channel with no impediment or binding. Rotor turns freely, the spring is strong and does not appear to have laxed over time or from loaded storage. There is nominal expansion or stretching of the sheet metal from removal of the front and back rail plates, purely cosmetic, does not affect the functionality. The M-1 L drum mod was active throughout the 1950's, which is as close to placing a pin in a timeline as I will likely get without provenance. Range spans from just after the war thru the late 50's. It is questionable whether this type of mod may have originated from “Trench-Art”, though possible. A question I would like to answer; did GIs bring the M-1 drum concept home or was this postwar Americana, like hot-rods, Harleys and “sporterized” K98s? I have photographed the drum with particular attention to the feed lips as the most interesting feature and arguably the most critical. The component is stout, solid, well thought-out, and well executed. As intended, it holds the round securely in position only allowing travel forward past the lips and not upward nor nose-up. My overall impression of the work is a fair amount of consideration/experimentation went into the design. I have taken measurements of the tower rail and placement on the drum body, then to try and determine if the drum has the potential to function properly, I loaded a round and measured from the bullet nose to the magazine catch retaining hole, this distance is identical as when a like measurement is taken from a Seymour stick. Overall, it appears to be a fully functioning drum intended for use in a full-auto M-1 and not designed for S/A. Obviously backwards compatible, if it can go F/A, it will handle S/A. Gary