I have several Eye Brand (Carl Schlieper) knives.
Fit and finish is terrific. Heavy duty backsprings. Nice chunky pieces of stag for the scales. I've got a couple of copperheads, a few of the small stockmans and large stockmans, a muskrat and a couple of toothpicks.
The large stockman, 4-1/4 inches closed is the most impressive IMO. It is built like a brick s---house, tremendous snap, no play in the blades at all.
Really nice etching and tang stamps. Heavy knife, heavily constructed. Really really nicely made.
Cuts great too.
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Case, well plenty's been written about Case.
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Canal Street - again, extremely high quality slippies but a little finer and elegant; less heavy duty than the Carl Schlieper.
If I was going into the woods with only one slipjoint I'd take the Schlieper over the Canal Street.
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As a working steel, I like the Schlieper carbon steel better than the Canal Street 420.
Fit and finish on the Canal Street is best of the 3 you mentioned.
I'm about to buy a fixed blade of theirs, looking forward to it.