Hi Andy; Neighbor is moving and gave me his A. Been sitting in the woods for a while but looks surprisingly complete and straight. Am new to the group so here goes. The plate on pass seat riser says it is model A40H 8470.The number on the block. EN377-62-43. Was unable to find frame # behind spring mount. Don't know what year. Can you let me know? It has a gas saddle tank with a Mack brass plate. Model R40, serial# 52 3. No box or 5th wheel. Probably used as logging truck. Has a single rear axle and air brakes. The rear diff is the common vertical ring gear, not the horizontal Mack style I thought was common. Thanks, Keith Update 6/14/15 Was able to talk to person who last worked the truck...39 years ago! His name was hand painted on the door. He thinks it is a 1952 model. Said truck had been in the iron mines at Hibbing, Mn before he bought it. He used it to pull a lowboy trailer for his excavating and gravel business. Have been working on freeing up the engine for the last month. Pulled the spark plugs and have been squirting various magic elixers into cylinders. Tried diesel and ATF, acetone and powersteering fluid, and Marvel Mystery OIl with either acetone or diesel. Has not worked yet. Have a chain wrench on drive shart near a yoke, with a five foot pipe cheater. No luck. Step on clutch and pipe falls so clutch and trany should not be the problem. Thought since the air compressor is bolted to gear case on front of engine, it might be stuck. So put "Magic Potion" in that too. Would think if engine was loose it should atleast rock enough to take up gear slack. Pulled starter and drive gear is well worn but ring gear looks O.K. Looked up part # in Delco-Remy site...yep big red discontinued. Looked in inspection plate on front of tranny. Back side of clutch and throw-out bearing look great. Put plate back on. Asked a friend about the "non-Mack" looking rear diff. He asked me if the Bulldog was silver or gold. It is silver. He said it must have been order w/o mack diff. If it was purebreed Mack it would be gold with Mack engine, trans and diff. Since I'm a "puppy poster" I can be uninformed and ask dumb questions. Wonder what this thing is worth? Anyway, having fun wasting time and getting dirty! Update 2/12/16 Received some info from the Mack Museum. Said the truck was delivered on September 30, 1952 to Mesabi Supply and Service in Hibbing, Mn. through the St. Paul branch. Doug said the truck was built with a single reduction RAS400 rear differential, the CRS76 had a 6.86 ratio. The two speed rear is a change that was made later. Now, all I have to do is wait two months to get the full package from the museum. Took a shot in the dark and sent an e-mail to the Hibbing Historical Society asking for more info on the business. The ultimate goal would be to get a picture of the truck as it was originally used. Worked with the last owner and we were able to get a title and plates. Had to take a picture from all four sides and had him sign the lost title form from the state. Licensed it as a 15,000# farm truck. License bureau lady said if I titled as a farm truck for the first year, collector plates would be much cheaper when purchased later. What should I license this as, how heavy.... Not sure if a collector plate is the way to go. Suggestions? Thanks, Keith