This past week I scored near new-in-box examples of the 6040 Fisherman's Filet and 6050 Fisherman knives. These knives don't seem to have serial numbers on them, like the 6060 Folding Hunter and 6070 Skinner knives that I have. Just making sure this is correct. I looked over both knives thoroughly and I can't find a number on either of them.

Thanks in advance for insight.