Some parts taken from articles over some trumpet sites. (Thank you for the courtesy)

Benge Trumpets- some orientations:
1x - Medium bore (M) .453". Comfortable and easy to play. Projects well and has good center of sound.
2x - Medium Large (ML) .460". Very brilliant and well centered sound. ideal for TV and recording, as "edge" reaches out to microphones.
2x+ - Medium Large Plus (MLP) .464". Takes more air than ML bore. Popular among dance band players.
3x - (ML) .460" Extremely flexible and responsive. Used in symphony and dance bands. Excellent for all types of work.
3x+ - (MLP) .464". Free blowing, with large full sound. Popular among players whose work requires versatility and finesse.
4x - (ML) .460". A flexible trumpet for players who like the sound of the 5x model, but with added resistance.
5x - (ML) .460" Large, brilliant and well centered tone. Has a slightly darker sound than the 3x. Freest blowing ML bore trumpet.
6x - Large bore (L) .468". Large, sonorous tone. Well suited to the powerful player.
I own a 5x - the bell diameter is smaller than my C trumpet and that of the Bach Bb owned by my quintet's 2nd trumpeter.
Benge C trumpets:
1c - (ML) .460". Designed to produce the "French" type sound. Very briliant and compact tone.
2c - (ML) .460". Excellent all around trumpet. Flexible and well centered tone. Ideal for all types of work.
3c - (MLP) .464". Very full sound, approximating that of the Bb trumpet. Bb players adjust easily to this model.
Note that I own a 2C+, a model not shown on the factory specification publication. Benge would create any combination.
Benge D/Eb trumpet:
D-Eb - (ML) .460". Brilliant tone. Excellent intonation. Very responsive. Used in many major orchestras throughout the world.
The D/Eb trumpet is the only model produced with a reversed tuning slide as the standard option, i.e., top tube sliding over the outside of the leadpipe. Also, the bell lacks the "Resno-Tempered Bell" part of the stamp.
The CG model stands for Claude Gordon. It is a large bore horn (.468") except that the bell is from a ML (.464") and is thinner. Benge workers at first buffed the bells until Zig Kanstul ordered thinner sheets. It is also believed that Gordon's first horn was configured with a smaller bore bell by mistake, but that he liked it so much that others were made and sold as 'his' model.
According to Benge's son, Donald, all Chicago Benges were made with a 3x bell.The Bubank and LA Benges were made in LA so more West Coast players seem to play them then did the east coast guys. There was not the wide distribution or internet to familiarize people with all these horns as there is today. Also, with LA and Vegas there were a lot of commercial type gigs on the west coast.
There have been many players who have played Benges at one time or another. Leon Merian (5X & 3X+), Wayne Bergeron (3X+, 7X), Timofei Dokshizer (3X), Carl Saunders and many others. They were excellent trumpets. The most versatile and popular model was the 3X, followed by the 3X+ and the 5X.
The Claude Gordon Benge has a slightly smaller bore size than the Selmer Claude Gordon - .468 as opposed to the .470 Selmer. Otherwise the differences are minimal. The main feature of both horns is the bell choke - the bore drops down to .464 on the Benge and .466 on the Selmer at the tail end of the bell as is leaves the first valve. These horns were extremely hard to make because the gauge metal was so thin. The Horns have been discontinued.