What is this???? Foundry mold? What kind of Part?

I found it in Mid-Coast Maine near Waldoboro at a barn sale last week. It had been used as a backing for a cast iron coat hook that hung on a wall. We removed the hook and saved the piece. paid $1. Seller didn’t know what it was. Ignore the holes which are from the hook screws and a place to hang the thing from a nail in the wall.

Details: 2” thick. 6” tall, and 12 1/4” long.
Inside radius of black area is approx. 4 3/8”
Outside gets wider from one side to the other.
End tabs are different sizes.

There are scribed lines indicating angles. From the left side going right (mostly black side), the angles would be 30, 120, 170 (a 90 is formed in the area with the 20-5). From the right going left, 40, 140, 170.

The angle scribes extend into the lighter colored wood. There are also two inscribed lines that start on the right and slowly get wider apart around the outer curve and flare out at the imprinted characters “2W109D”

The black areas are painted black.

The other side is also labeled 20-5 and has a beveled groove between the light wood and dark area.

There is no obvious wear from rubbing or scratching.

Thoughts:
20-5 is one “stage” or piece in a series....it is the 5th one in the 20’s.....

2W109D....2 width with a 109 degrees/diameter?

used as a key or jig in a machine.

Boat Lofting tool.

Textiles, hat making, fabricating template?

bending tool.

map making standard.

Musical instrument jig?

Foundry Mold, part number 2W109D, shelf location 20-5