This disc is undated but I presume it's approximately around the similar model. I also hav emore information on the Black-on-Green disc. I found one with a metal core. the problem with this is two fold. First it's undated, second I had assumed that the metal core was an early design. So either this is not the case, or the Black-on-Green goes back further than I had estimated. I have not accounted for this incongruity yet. Perhaps with more confirmed dates this will explain itself. [Contributions are welcome if you know more.]
Red Top on Yellow: Unknown, assumed to be first disc1943?
GEM Mutoscope Disc: 1945?
Red on Yellow: 1943, 1944, 1945, 1946, 1947
Red on Beige: 1946, 1948
Red on Unbleached: Unknown 1940s?
Red On Blue: Years 1947
Teal-on-Unbleached : Year: 1948 (assumed)
Blue on Blue: Year: 1948
Black On Red: 1948
Black on Green: Years:1951,1953 - 1955 (also had metal core variant)
ESO Mutoscope Disc: 1950s?
Mutoscope Black Label: (45 rpm) Years????
Black on White (45 rpm) 1957, 1959
Blue on White: Unknown assumed 1960s?
Black on Yellow: Years 1964
Black on Red: Unknown assumed 1964?