Help ID Forged Fixed Blade

[kootenay joe]

Here is a unique forged knife, 10 1/2" OAL. A piece of the steel extends above the blade and is folded over and pinned through the antler tine handle. There is also a tang that goes into the antler core.
There are maker's marks: one looks like a "Joker" image, there is "75" and in a circle "I S O R/BY"
"BY" might be maker's initial and "ISOR" = eyesore ?
Anyone recognize this style & markings ?
kj

[btrwtr]

I think this is the mark of John Sorby. A Sheffield tool maker.

[Cicatriz]

This looks like half of a set of Sheffield made shears.

Maybe sheep shears, probably garden shears.

Someone turned a broken shear into a knife.
Common and very useful. Even here in Texas.

[kootenay joe]

Thanks for this help. I am impressed that you were able to ID this marking. I have sheep shears and now that you mention this, i can see the half shear blade in this knife.
I have more admiration of this knife now knowing it's origin is half of a sheep shears.
kj