I tend to prefer combination locks because they seem to incorporate more intricate work, and this lock is a good example of that:
Vintage 1869 Patent H.L. ARNOLDS COMBINATION LOCK - A vintage high quality brass combination lock marked on the front "H.L. Arnolds Pat. May 4th 69". It measures approximately 2 1/2" by 2 5/8". It's in excellent cosmetic condition with nice patina. The number 267 is lightly scratched on the left side of the front. The combination wheels spin freely. I do not know the combination. - eBay
Not having a key or combination is a real problem when it comes to collecting locks. Of course the price for locks that you can still open is a little to a lot higher depending on how rare a lock is. This lock has no combination and still it has gone for $322 (Plus $5 shipping) with a lock like this and a bit of time, one could figure out what the combination is by simple trial and error. And I would start by trying the number 267...
Unfortunately, this lock was a bit too expensive to add to my collection. That is probably for the best, since I would most likely have messed it up by polishing it!