|It was made by United Specialties and had the block U at the bottom of both the front and back slide, but the other slide markings appear to be identical to the Colt drums, including the comma after N.Y. on the back slide and no drain slots.|
Just to avoid further confusion, the United Specialties Co drum does have a comma after "New York" on the back cover, where as the Colt drums do not have any punctuation mark. So even though there is a comma after the period in "N.Y.," on the USCO drum back cover, the addition of the comma after "New York" distinguishes it from the Colt drums.
Richardson seems to be at odds with the notion any Worcester drums came with a bright steel rotor. The way rotors are swapped in and out on these pre WWII drums, it is difficult to say for sure what the deal is. Hill's book confuses a no "NO" marked drum with a Worcester drum, thereby making 4 types of Worcester drums when there are only three types. So the nickel rotor that Hill sees in what he believes to be a first pattern Worcester drum, is in fact a final Colt drum.