Back in the 1960s, I saw a historical display at the Ohio State Fair, I think by the Soil and Water Conservation folks, showing some old clay field drainage "tile" in the shape of bricks with some language molded into the flat side of them about John Wilkes Boothe, the Martyr.
These were likely locally made near where they were dug - lots of clay in Ohio for bricks, tile, etc.
They were made in a form I have never seen before or since, oblong rectangles, with one long side shaped into a trough from end to end. They were installed in the dirt, end to end, laid one on top of the other, troughs to the inside, and so creating an open tube running through the middle.
The design reminds me now of how the lady at Subway makes my sandwiches, with the long bread loaf cut through the middle, and then some bread scooped out of the center (creating a tube) so the ingredients will fit in the hollow!
I suspect they were homemade by some southern sympathizer who didn't offer them for sale or show them off, just put them into the ground on his farm. Round clay tiles (the usual type laid by hand digging to drain wet fields in the the old days) would have to be extruded, and require some sort of machinery and so would be a manufactured item, but any farmer with a clay pit on the farm could make rectangular bricks and fire them - we had some chimneys made from home made brick on the farm where I grew up.
Anyway, such "brick" would certainly make an eye stopping part of a display, eh?