It looks very much like a timer made by Garrard of Swindon, better known for their record player turntables etc. During WW2 they turned their hands[ATTACH=CONFIG]221016[/ATTACH] to making such devices, used in various time delay munitions it would seem.

Pic of one that I picked up at a car-boot earlier this year, since flogged on..the new owner tells me that it still works a treat!