Engine Date for Tubman

[Ironrod]

I was able to get part of the date code on the truck engine I brought home.
S 4 and the no other letter, after that a box with a 1 inside. I assume Oct. 10th would be correct, not knowing the year.
Is it possible the box containing the 1 a rebuilders mark? I live about 50 miles south of Jasper In. Jasper Engines rebuilt many engines that were sold in our area, not saying this is a Jasper engine. After research, I was unable to find any company mark with a box with the 1.

Bob