I do not see anything missing. You may need to be a bit more specific.

If you are talking about the screw hole, that was where a music holder (lyre) could be attached. They are usually missing, there are replacements, and nobody uses them anyway.

The mouthpiece missing also is not a big deal. Most players already have one. If not, a more recent piece is usually desired, rather than the original one.

If it is a B flat soprano, it is a 1,200 dollar or more instrument in playing condition.

If it is a key of C, probably a bit less, because music is not written for them today. It is keyed the same as a piano or violin.

I use to do a lot of pre setup work for Cybersax who was in Tulsa. I would then ship horns back to the owner of Cybersax and he would do his wonderful silky setup. I still use a number of his "secrets" myself.

That was 12 years ago now. Wow.

Saxquest in St Louis.

Tenor Madnes is Waterloo Iowa.

PM Winds in Chicago

Those are who use to compete with Cybersax.

 https://pmwoodwind.com/product/buescher-4/

Here is an overpriced example at PM winds.

He is evidently in no hurry to sell it.

I myself live in Cincinnati.

This is the type of work I do in my leisure time now.

Expect it to cost at least 500 bucks to get it all clean and playing nicely.

If I saw this locally, Id pay up to 400 bucks for it as is. Put my time and effort into it, the 500 bucks or more you pay a retailer, and Then I would  have a 1200 dollar horn in the 900 range.

My nitch is I dont have to pay myself labor and I dont do it to pay rent or employees.

Good Luck