Take a look at the left hand side of this U.S. Internal Revenue 50c stamp. There is some sort of print in the ink to the left of the stamp which I'm unable to make out. Hoping a stamp detective here can make out what it is exactly. I've been unsuccessful thus far. I'm uncertain as to what the design is, orientation or what it may say.
Here is a link to a large image for manipulation and a closer look. You may want to download it.https://drive.google.com/file/d/1xg...?usp=sharing
TOP LEFT LOW RES:
UPDATE: Another clue may be in the "50" at bottom...