It might help if you include a link, but I would guess that the item you found is an upgrade feature for the old-school Ace Nautical Commander radio. The Ace used to be a nice radio for scale boaters, since it was built as a modular, customizable radio. Most of them had two throttle sticks and a separate rudder stick, instead of the more traditional two-gimbal setups we usually use. This was great for RC tugboat skippers, who would use the two throttles to improve the maneuverability of their boats. It also could be upgraded with features like buttons and switches and sliders and dials and dual rates and end-point adjust and other cool features that weren't easily available, many years ago. It wasn't all that great for RC combat, though, since we never had any use for dual throttles and the rest of the control layout was poop for combat ships. It failed to keep up with the times, and eventually got swept into the dustbin of history. Except that tugboat skippers still like it, so I guess parts are still being made for it.
