Lettered Bricks

This font is one of the simplest we can make. It consists entirely of the standard 1x1 brick with printed letters on it. But even if the technique is simple, getting access to these pieces might be tricky. As far as I can tell they were produced in a specific, pretty old, set - never to be seen again. Please correct me on that if I'm mistaken.

Since they're a standard 1x1 brick they're exactly three plates tall and easy to use. They seem to have been produced with blue print on a white brick only.