I have bought worse just to have an example of a mark or pattern. If you paid a smaller amount for it than you would have for an as-new example proportionate to it's condition, you did OK.
I recently bought a group of four (cheep) to get one of the four, a rough example of a Camillus made Sears Fulton Barlow circa 1943. But even the three other stinkers I had to take along for the ride are interesting in their own rights.
The object of my interest actually seems to be better than I had hoped (for a 67 year old knife that sold for twentyfive cents new). With a bit of cleaning it will actually be presentable, though never a pristine collector knife.
The first "gimme" turns out to be a Pal Blade Co. utility "mountain knife" of WWII vintage with good blading, though the jigged bone covers are cracked all to heck.
The second "gimme" is a 2 - 3/4" mother of pearl pen bladed jack whose marks I haven't been able to decipher yet.
The third happens to be a Schrade Cut Co. yellow pearl pyralin two blade jack (pen blade broken).
They aren't display knives, but each is unique and an example of the type. And still a good user.
All of these together cost less than a happy meal.