[Scott]

In the 1970s use of the word computer had quite a different, more literal meaning: it was something you used to work things out.

This Scalextric Speed Computer was used to scale up the lap time of your slot car into a 'real' speed. The reverse side had all the available track pieces with eth length of each lane.  Kids were expected to find arithmetic undaunting back then.

I think I probably used it once or twice, but I've kept it for 50 odd years.

[ABBO]

I still have mine... somewhere...

I used to love it as a kid. Nothing better than working out that Niki Laud's Ferrari could lap my 40-odd foot track at an average speed of close to 200mph 

I joined at "proper" slot car club when I was about 14 and couldn't believe the scale speed of a slot car with a metal chassis and vac-drawn body. Probably about 1000mph