Different brands of different horns have their quirks. One quirk on some Geyer style horns is that they may have a squirrelly high B-flat. Usually this is attributed to an acoustical factor related to the first valve slide of the B-flat horn. While you don’t want to develop a complex about it, this is certainly a note to test if you are looking to buy a horn of this type.
As a background note on this, one of my former teachers had a Geyer horn as a young professional. He had some questions about the horn over time and had two different, very well known players try the horn to test it. One said the high B-flat was fine and the other felt it was unusable. The truth was probably somewhere between the two but his confidence in the note was not strong and soon after he sold the horn. The right decision? Maybe–as he had developed at the least a complex about the note, his confidence was down.
Makers have tried to compensate for this note various ways. One of the more visible is to have a rounded slide as are seen for example on Yamaha horns. Slide inserts can also help stabilize the issue. The problem relates to a nodal point in that critical area is influenced by something in the design of the horn so that the stability of that specific note is impacted negatively. The fix is somewhat variable in terms of success but is one that must be addressed if it is an issue on your horn.
If you are unsure about your high B-flat and play a horn of this type, have another player or teacher test it and get an opinion. It could result in your developing a full-blown complex but it also may put your mind at ease. Hopefully it won’t end up being a confidence shaker, and the road will be opened to you to have more confidence in a critical note.
If a horn does not have a high Bb, you may be able to help it if you love everything else or it is a great deal or whatever, but on the whole you are probably better to just walk away.