Saw one model with a dual range ??TANK?? transmission.
Not a tank transmission, but a Sherman Step-up (or possibly a Step-down) dual range attachment that either raised or lowered the gear ratios. Manufactured by Sherman Brothers.
We had several of these tractors back in the 50s and 60s. They were crude, underpowered, and not really heavy enough for really "big" farming. Their main selling point was the Ferguson hydraulic system with draft control, and later position control. They were perfect for the typical row crop farmer in the South who grew corn, cotton, and peanuts. Most Ford dealers also sold Covington, Pittsburgh, and Dearborn implements. When the Hundred Series tractors came out, a farmer could work a pretty good acreage with a couple of 600s and a couple of 8Ns. Any of the tractors could be used to plant and cultivate, and the Hundred Series tractors were no slouches in the power department. I still use the Covington planters, mounted on a Pittsburgh cultivator that my fil bought in about 1957. He farmed his 50 acres, plus about 40 more rented acres, with an 8N and a 600. I still have his 600, and intend to have some work done on it this winter. The 600 (actually 640) is about twice the tractor an 8N is when it comes to plowing and heavy pulling. I can still use those nearly 60 year-old implements on new smaller tractors because the three point hitch remains basically unchanged.
Late model Kubota pulling old Ford/Dearborn 2 bottom breaking plow from the middle 50s.
1957 640 Ford and Pittsburgh cultivator plowing food plot
Same rig with Covington planters mounted on the cultivator. More affluent farmers would have two cultivators so they could leave the planters mounted on one, and use the other for cultivation. My fil only had the one. He only planted Corn and cotton, so he was through with the planters in late spring and put them away and used the cultivator for plowing out the crops.
600 under the shelter.