Found it! Nice rifle, badly treated, and seemingly used hard. Still, a golden age gun with fine carving and nice preening bird patchbox.
Chances are, this one has had the barrel cut back a couple of inches when it was converted. It should have had a 45 inch barrel, as that was a length Beyer used on his smooth guns, which this was/is. Good untouched condition and a worthy addition to any collection.
Wonder if the lock was actually replaced or just converted? Beyer used both English and Germanic locks on his guns from his earliest work. Would guess that this is one of his rather early pieces and it compares well with one shown on an antique gun website not too long ago.
As to the estimate, who knows how the house determines the limits. This gun will go for far more, I suspect. The J. Small gun at the last Julia Auction was estimated to gavel down at 40K to 60K and it brought 180K. Happily, this gun is not in that league.
Thank you for bringing it to our attention. Good luck, if you go after it!
Dick