Found this listed as a 1953 OC-3 on Craigslist. Interesting features are the 4 rollers and the name plaque on the track frame " Chicago Pneumatic" Also I'm wondering if the grill is a factory guard? It appears to be the same stamping as the early Cletrac pattern. Looks too well made to be a home fabrication. The under carriage looks to be in great shape from this picture. Ad says it's been on the family farm for last 25 years.
http://seattle.craigslist.org/sno/grd/3112479222.html
(http://pic20.picturetrail.com/VOL83/533924/19016921/403257869.jpg)
That track frame was off of a Chicago Pneu. rock drill. A lot of the drills used Oliver undercarriage parts. I think somone just made that grill guard out of a piece of a Cletrac grill. If you saw it close up, I don't think it would look as good as you think it does.
Strange, I just found another one of those Cletrac pattern grills on what looks to be an HG on Craiglist. Could it be coincidence that both of these were home fabricated?
(http://pic20.picturetrail.com/VOL83/533924/19016921/403437962.jpg)
http://seattle.craigslist.org/tac/grd/3146447118.html