I have a friend who’s selling an old Bach 42T horn. The valve does have the O.E. Thayer stamp on it. No dents. The slide moves reasonably well and there’s minimal lacquer wear/oxidation around the bell edge and on the slide. Valve has pretty good action too and seems to still have a good seal.

Can anyone give ma a ballpark on what it’s worth if I wanted to make an offer?

I would add photos but have never posted in this forum and have no idea how to. Basically from far away you’d likely not see any of the wear.

EDIT: https://photos.app.goo.gl/6F1KzHeSCuKwctdu7

Hopefully that works.

i think bachs are VERY dependent on how it plays. if you have played it and its exactly what you want, id say you can be happy to pay UP TO 2.3k usd for it. a normal 42B in good condition and plays quite well sells for 1k-1.6k. (older corp, mt vernon horns command a premium). I think a good market price for the horn you described places it at like 1.8-2k for it. There's quite a wide market for bachs. if i played it and found it to sound good and be in really good condition, id be happy to pay 2.2k

BUT sight unseen based on your description of probably 7-8/10 slide action, 8/10 cometic condition, 9-10/10 valve action and seal, , me personally, i would offer 1.8k. since you know the horn and have seen it yourself. you should play it and get a feel for it. but based on what you are describing, i would say the horn value sits between 1.8-2.2k usd.

if you toss in photos in a google drive,. you should be able to paste a link in here

I would definitely check the condition of the valve core. They are aluminum and early versions were prone to corrosion in the long term. Aluminum oxide is white, and here you can see it forming in a few areas: