In the course of my expeditions, I have mentioned occasions of finding one random brick in a sea of another type.  I also occasionally find broken bricks or blocks that have just enough information to know they are different but not enough to know what they are.  Sometimes, with a lot of digging, a full size example is unearthed.  Most often, I just have a broken piece to ponder.  With some sleuthing and mediocre hangman skills I can figure out what some of them are.  There are the examples I have.  Maybe you can fill in the blanks.

This one, I figured out using the Ohio Marked Bricks Book.  The script in the brick made it easy.  It is a Ferris Brick.

This one, is also easy, Capitol.  No rocket science there.

In the example, the second part is easy Detroit.  The first part, I have no clue.

This example is hard to see.  The bottom is Crown.  Above that is O.

This one we can see CK Run Paver, it is looks like a 20th Century Paver in size and color.  The mystery remains. (Update: I found reference to a Rock Run Brick Plant in Ohio, maybe this was a Rock Run Paver? )