When fully opened it's just oven an inch, too small for an automotive dust cap puller. And the spike is, for a better word... delicate. It's more of a small knife then a hook for prying, dull on the front and razor sharp on the rear. I'm still thinking it's some sort of food processing tool or leather hide puller/cutter.

Is it a farriers tool? If so I would bet/guess that it has been modified by adding the spike.

Otherwise, if a fishing tool, does the spring loaded feature help?

Chilly

Farriers tool is what I was thinking.  For small hoofed animals. Sharp edge for shaving the hoof

The spring load feature works just fine, as seen in the pics that is it's natural "open at rest" position. The small blade is razor sharp but thin and faced backward, so you would cut with it by pulling towards yourself. It just feels like a fish processing tool, it doesn't seem stout enough for sheep or goats.