Not sure, maybe mount for another cylinder for added rear attachment.
I need a picture with the more of the push arm to confirm my guess, and with what I can see I could be headed the wrong way.
Garwood dozers had pivot point real close to the trunnion in the push arm. There is screw that spanned the pivot, the farther the arm is from straight would raise that corner of the blade as a tilt for the blade. Sorry no picture and not very good at explaining it all.
Short answer part of a tilt for your blade. But the picture does not take in enough arm to confirm, so a guess only.