My Complete 16 gage Baltimore, has a trigger plate as you illustrated in Figure 11 of your 02/1997 article in "The Gun Report".

However, the trigger plate milled cut in the receiver with the missing plate is slightly tapered as it goes forward, without the two lobes on either side of the front. I believe that this is the distinction that you refer to as Model 1902 and 1904. Please correct me if I am missing something. Both of these are "A " Grade.