I don't believe they were supposed to have. All of mine (20+) from all vintages have a symmetrical ground edge. Sometimes the bevel is not perfect side to side, one a more acute angle than the other, but with use and normal sharpening between uses, it usually evens out. I have skunt (Tennessee talk: past tense for skinned) four bucks with one so far this year, and yes, they are the perfect skinner knives for me. Larger cuts are done with a 165OT. I used all stainless Safe-T-Grip series knives last year, but you just can't beat a good carbon steel blade. Resharpening, if done often enough, and with a fine hone, does not remove much metal. My original 165 (Schrade Walden #16239) does not show any appreciable blade loss after more than thirty years of use.
Codger