Pay attention to the mouthpipe that goes from the mouthpiece receiver to the tuning slide, and to the area around the spit valve. Pull the tuning slide and try to see down the mouthpipe. If any of these things are evident, these parts may need to be replaced at some point.
if you can't tell, like I can't, don't waste your money.I would guess that he bought them because the market is flooded with H. I am going to guess he is selling the average ones and keeping the one that really sings for himself!Obviously no one needs 5 180S37's all at the same time!Don't base your decision on that scale alone, but it could help you decide. When you pull them out a half inch and let go, do they pop back to position, or close to it? Can you see evidence of corrosion anywhere inside the tubing?You might also find that certain valve combinations are always a bit out, no matter which notes. This is hard to see, but you might be able to get some clues looking into the leadpipe, especially at the mouthpiece end.
That may eliminate the ones with the higher serial number because some people think they are of lower quality than the earlier ones. I would (1) bet that there are subtle differences in the horns and (2) would strive to find those differences and choose the one that most suits you, no matter what the serial number is.