The Los Angeles-era Benges are very good horns. You have a horn built late in the time Benges were manufactured in Los Angeles, after which UMI bought the product line and the quality went downhill.
If you are interested in having the horn rebuilt or repaired, the best bet is to contact Kanstul Musical Instruments
www.kanstul.com in Anaheim, California. The owner, Zig Kanstul, was the former Benge shop forman, and his company owns the original Benge tooling. They make, among many models, horns that are essentially the original Benge models and they are very highly spoken of. He would easily be able to restore your horn, make any necessary parts, etc.
You can read more about the history of Benge here:
http://www.dallasmusic.org/gearhead/Benge.html