It looks a lot like a hand crafted seam picker for old wooden boats. But considering how many things got repurposed into seam pickers, I wouldn’t bet that, that is what it is.
I initially thought it was modified from a Phillips Head screwdriver by grinding down one of the flanges. However only the rear flange narrows and the others are flat and even thickness, so that seems unlikely.
I’d be looking at traditional tuckpointing and plastering tool sets. Each craftsman would make or modify a tool to fit their own hand and preferred method of working. The modern mass-produced stuff is pretty different, so its probably part of a bespoke tool kit.
Hmm… that’s intriguing because it was in my basement along with a lot of stuff that clearly is for plastering/ painting/ stucco. Only so far nothing that looks close.
I can only access the first image. Looks like it’s used for prying. Judging by the dimensions in that one photo, I’ll say it wouldn’t be strong enough for much more than cabinet making or upholstery. For purposes that require greater force (automotive, etc.), I don’t think it would hold up after repeated use.
My dad had a similar tool with a small v-shaped notch in the blade that he used for removing & reinstalling the springs connecting brake shoes on vehicles with drum brakes. Worked like a charm!
Can’t see any great detail in the first (and only) image, but there are a lot of tools made with an offset handle and many others that started out as something else and ended up looking like that.
I have some tools with similar shapes in different sizes, they all serve as pry bars and picks and spreaders and packing tools, or whatever use is needed at the end of an offset shaft.
So what we have here is a “5 in 1 Offset Multifunction Tool”. Which 5 functions were originally intended is hotly debated among tool enthusiasts.
ETA: The two other photos are now available. It does look like it was made from a Phillips head screwdriver. Purpose still variable.