CAST IRON SURFACE PLATES 4- $75.00 ea. Columbus Ohio

[seasicksteve]

Those are not surface plates. They were originally the bed of a paper cutter made by the Challenge Machinery Co..
I used to service this equpt.
No real surface spec. The bed supported a stack of paper (for printing) the a guillotine knife came down to trim the paper to size. I you look at the printing equpt auctions, these are readily available. Challenge "end of life" many models over the last 10 yrs

I agree that these are from the printing/ graphic arts industry. Not sure that they are cutter beds. They appear too small to be from any cutter I have encountered. My thought is they are small bench top makeup stones for letter press. The type setter would place the chase on this stone and set the form and lock it into the chase with a wedge or quoin. I grabbed up one of these a few years back pretty handy around the shop