Larry,
Any chance you know the serial number of that first-five Chicago Benge? I ask because I have seen conflicting information on what the first number was. this page from the trumpet gearhead
http://www.dallasmusic.org/gearhead/Bengedata.html lists the first trumpet as number 525, but I have spoken with Donald Benge who told me it is number 500. I haven't yet heard of a trumpet below 525.
I also own a very old Chicago Benge, #56x, with an interesting history. The guy I bought it from bought it used in 1949 with the help of Vincent Cichowicz, his trumpet teacher. Vincent Cichowicz played in the Chicago symphony with Schilke, who was helping Elden Benge build trumpets in his basement. The new owner brought it to Elden Benge who fixed it up and re-lacquered it. The owner also met Schilke, who gave him a mouthpiece to use in 1950. The interesting thing here is that Schilke didn't officially go into business until 1956. The mouthpiece is in the case with the trumpet. I have verified parts of this story with Donald Benge, who remembers the owner. I would really like to contact Vincent Cichowicz for further verification if anyone knows how to contact him.
And oh, buy the way, mine has a standard third slide setup, and I believe that is original. Elden did supposedly make them for a period reversed, but I have never seen serial number range where that happened. I also own a #3xxx Chicago, and it is standard configuration as well.
Steve