600, 632, And 685 Questions

Hi all

I have three stamps that all seem very different from the regular issues.
I did notice that all three of these stamps note cracked plate varieties.
I am not sure what is referred as a cracked plate issue.

The 3 stamps are a 600, 632, and a 685

The 600
[the lower left 3 has a line to the left and a dot to the right]

The 632












[the united states p all have raised letters above them]

The 685
[the lower 4 has a line under, a dot to the right and a larger marking to the right]

These all seem a bit different and I would appreciate any thought on these three stamps

Dan

These 3 stamps were printed on the Stickney rotary press. On the flat plate press the plates were polished by hand after ink wiping station. The polishing helped to ensure that the plate was completely inked. On the Stickney press the plates were simply wiped with a metal squeegee type blade that was far less effective at getting the ink into all the recesses in the plate and also at cleaning the top (unprinted surfaces0 of the plate. These stamps appear to be ink distribution anomalies which were common in early rotary press stamps.

Great explanation Russ. Thanks.