This picture, taken in 1967, seems to show some piece of small equipment doing some kind of landscaping. Is there perhaps a blade coming out the front of whatever he is sitting on?
Based on the answer received, I found a picture of a trencher from the 1960s:
I emailed Thomas Berry, the Archivist and Editor at the Historical Construction Equipment Association, and he said "From what I can tell the machine is a miniature crawler tractor for work in confined areas. Can’t tell what the attachment is on the end away from the camera, but it’s likely a bulldozer blade or possibly a trencher for digging a narrow trench."