That's either a rebuilder's ID tag, or possibly something a fleet owner used to identify their engines for inventory purposes. I've seen similar tags attached to engines Sears sold as "remanufactured" back in the 50's. They were usually rejects from other rebuilders with big overbores and deep undersizes on the crankshaft journals. Other mass merchandisers like Montgomery Ward also sold reman engines back then.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!