Dear Jack,
We use the Almen strip block for our shot peen process and some of our Almen blocks are worn and old and in need of sorting.
Can you please let me know?
What is a bridge gage?
What is the best way to check the Almen block flatness?
How do you check it?

Thanks in advance

The Almen blocks can be re-surfaced by grinding to get the surface flat again.

The surface should then be checked with a dial indicator for flatness.
There is presently a tolerance for flatness of 0.1mm according to SAE J442.
You can also submit the holder to a lapping machine for further confidence.

I am not familiar with the term bridge gage.