Washington Stamp Overprint 1

Dear sirs
Kindly any information about the overprint on the below stamp ( 1 )
Best regards

Not an overprint, just part of the machine cancel.

Thx a lot

Here is a similar cancel for reference. The cancel was just applied differently when being fed through the machine and the numeral 1 landed on the stamp. No telling of where the stamp was exactly placed on the cover.

To build on stallzer's excellent reply, canceling machines often had a machine number in the dial or killer. The example stallzer shows is an International machine. Yours is from a Barry machine, like these:



Yes, when the machine number hits the stamp it can cause some confusion. Soaked stamps often lose the context of the full cancel. Here is a tightly cropped version from a cover included in the scan above. It looks like a re-value at first, but it is only the machine number!



Here is a page of numbers from an old collector's stockbook. There is a page of alphabet letter cancels too. Fun stuff!