Sorry, but this is one I haven't even begun to think about yet (the closing date is Jan 2, and there are other puzzles on shorter deadlines and that's not to mention everything that's happening in the real world!)
Just a thought - maybe 'abacus' rather than 'meter' might be a fruitful line of enquiry? I'm sure this will be discussed in the days ahead.
To help others without sight of the original, the link to the puzzle and the instructions is:
http://image.guardian...9/12/14/1960dec20.pdf