Gas fired Add-A-Foot
That particular item you are asking about is a 12" gas fired "all-purpose" cooktop.
It can be used as a griddle but can you imagine the mess with the grease everywhere?
More often, they were used as boiling plates where you could put a pot or pan on top and boil water, cook soups, or cook items in large heavy duty chafing style pans.
Most often they were seen as a triple unit on top of a 36"range and came in different configurations. All the major manufacturers made and still make these cooktop ranges.
These small ones would sometimes fit between 2 different items in a cook line but as a 1 ft unit, their versatility could hardly be realized. The nice part about these types of griddles was the heat retention of the griddle surface. Once you got your food boiling, you could throttle back the gas or electric and cook at a nice even rate.
The picture below illustrates the Hobart CR-40 which is no longer made. The 12" model was the CR-44 just to give you an idea of what the electric model looked like.
Rule of thumb on griddle heating is they heat up a degree a second and cool off a degree a minute.
