Well, I googled beaverboard and about half the entries referred to Grant Wood's "American Gothic", which was evidently painted on you-know-what, which makes me think that anybody who wants to see it in person better do so soon, before it disintegrates into something you'd find at the bottom of a box of shredded wheat. This fine product appears to have been commonly used in lieu of canvas by cost-conscious artistes, in addition to its application as a wall covering.

One of the wall covering uses was in lieu of ceramic tile for bathroom and kitchen wainscots. It was manufactured with "tiles" embossed into the face of the beaverboard and field painted to look just like real tile --at a fraction of the cost. The samples I got today show no such embossing, and as noted previously, bear no identifying marks.