What is this?

I got this several years ago and I still haven't found out what it is used for.

 

The 2 sides are at roughly 170 degrees to each other with about a 1/8" gap between them. Overall length is about 14"

 

This may be a stretch, but I have seen plastering tools that have a metal edge cut to the shape of the pattern you want to have on your wall/ceiling. The ones I have seen are handmade and are mounted to wood used as the jig. You can draw out the pattern into soft plaster. They look like this:

 

Interesting idea, but it seems to me that the handle would be in the way.

 

Some are used directly on the wall, but others were used to make the piece on a bench and then mount it on the wall, but it would be impossible to keep that tool registered with the piece to make a perfect pattern so probably not related.

 

SHOUTOUT TO @anundverkaufen, you know what a lot of these tools are!!!!!!