Picked this up today...really pleased with it! It's a big knife...4 3/4" long...nice bone, old shield, 3eyed, straight-line stamp.

I have a question though...some straight lines have "rustless" on the reverse side of the tang...and some have an eyeball...does this help narrow the age of the knife?? The couple knives I have with an eyeball on the backside of the tang look older to me. I'm just curious when the "rustless" started...and also when the eyeball ended??
Trying to narrow down the timeline of these older eyes seems quite tricky.

...but I love em'!
Thanks,
PerryWayne