Without pictures and knowing the exact condition of the instrument it is nearly impossible to get it assessed. I will give it a try... If the instrument is still in playing condition,(all pistons move, all slides move, the are no leaks...etc) and if it is still in good cosmetic condition it might be worth something. If not you might as well make a decoration out of it.

If you want a good idea for prices just look on eBay and you might find a similar model. In my opinion used trumpets seem to go around 75$ if they are playable.(for beginner models) Pro models go up alot more, especially if they are rare. It might be worthwhile to take it to a local brass repair technician and get his opinion. Just ask him is he can give you some advice.

Good Luck.