Older wood-handled folding saw lock

[Sturubu]

I picked up an older folding saw, and can't for the life of me figure out how to release the blade to fold. It was open when I bought it, and I figured it just needed a good WD40 soak, but on a closer look it seems to be missing a part or two. There is a notch on the back side, but otherwise nothing evident as far as how it should unlock.

Are there any standard type lock mechanisms that anyone is aware of?

 

[Hickory n steel]

It looks like a broken lockback.
As if the end of the lock bar which you push to fold it has broken off.

 

[Sturubu]

Thanks, that makes perfect sense! I suppose I get to take it apart after all...

 

[eveled]

If you decide to get a new one. Opinel makes2 sizes of folding saws that are awesome.