Duke,
It is believed the Griswold Small TM skillets with grooved handles were produced from c1952-1957. This is info from research by Steve Stephens, myself and others. It is probably more accurate than either the Blue or the Red Books. The Small TM was produced from c1939-1957; first with the early handle, then with the late handle, and finally with the grooved handle often referred to as the late grooved handle.
Roy Meadows