Woops! Grot Logo re-do...
While I may not know much about the dark ages of slot cars, I have spent a number of hours in front of my television watching BritComs. The "Grot" logo that is seen engraved into the chassis is the same font and shape as that used by Reginald Perrin in the show, "The Fall and Rise of Reginald Perrin," 1976-1979. After faking his own suicide, Perrin, played by Leonard Rossiter, started a shop that sold only useless things. The shop was named, "Grot," short for "Grotty," short for "Grotesque." The amoeba shaped outline around the word "Grot" is the same shape as Perrin's sign for his store. This may help to date the chassis, as they could be any time after 1977, (the first year that the "Grot" store appeared in the show, but not before. That's my 2-cents worth from this side of the pond.