The product is SHAPE brand Sheet Glass, and the product description says it is "for use in picture frames, replacement window panes, painting, and other crafts

The product is SHAPE brand Sheet Glass, and the product description says it is "for use in picture frames, replacement window panes, painting, and other crafts and household projects", which I figured was enough of an endorsement for this use case. Not safety glass, but maybe I'll swap it out if the whiteboard ends up getting a lot of use and I keep it around longer term. This is essentially a prototype, so definitely open to changing things as time goes on.