Mystery graphic on TM9 covers

[pfarber]

I noticed this little gem on some TMs.

leaf1.PNG (136.78 KiB) Viewed 12735 times

leaf2.PNG (77.42 KiB) Viewed 12735 times

Note just under the "TECHNICAL MANUAL" line... what looks like a clover and a leaf. Its also on other TMs I have:

machinist.jpg (63.06 KiB) Viewed 12735 times

This TM is printed 1941 at the US Government Printing Office.

It only seems to show up on TMs dated 1943 and earlier. Not sure what it is, or what it means. A quick way to tell what printer it came from??

Any ideas????