Launched in 1969 this machine was built through 1979. The collector half carried on until the end of operations as part of the late model friction drive series. The term UniTrol was coined by a marketing manager and it stuck. The term denoted the traction system that was operated with a single control lever. It was a breakthrough in operator simplicity, as most competitive systems required clutching and shifting actions. Gilson did go on to reuse the term on other single handle friction drive designs.The vast majority was built as 26-inch units with a few of the 5 HP models scaled down to 22 inches in the early years. Originally offered in 5, 7 and 8 HP versions a 10 HP engine was eventually part of the line-up. These machines were generally 3 speed units.
Variations include a 4 speed control handle and a walk-behind tractor version that are both explained below. These variatons exist individually or combined into various models. The signature features mentioned below apply.
The signature feature of these machines is the big dimple in the back bottom panel. The pattern of the bucket side wall stamping is also indicative of this machine family but was also used in the late model friction drive machines. There were high and low rise versions of the bucket. These pictures illustrate the migration from the crimson & beige color scheme to the crimson and black in 1977.
You can read more about these machines here.