Looks like an old, OLD Hofner beetle bass, with all the hardware removed. I've never seen a guitar like this, but I never looked for one either. The curved bulge at the top of the headstock is quite unique, and it makes me wonder if that was a custom modification. Same players like having weight at the top of the head and I wonder if someone had this cutom built or added that themselves.

It's either a Hofner, or an early Hofner knockoff. Can you put up a pic or two of your grandfathers?
John 3:16 = Truth

Sight reading tableture = Guitar Hero for real guitarists
Spoon + Pen = Spen
Quote by HJS >.>
What would be the best bass string size to play something like Slipknot

Quote by Brad_Bassist
No strings. If you're playing Slipknot, you don't deserve strings.