Hi;
I picked a Rev Counter up from eBay (listed as S/H but never used).
I thought that it would be a simple case of wiring it up to the Ignition Coil, however upon receipt whilst there are two electrical cables on the back these appear to be for the internal light. In the centre of the rev counter it looks like a Speedo Connection.
My guess this is a mechanical Rev counter and therefore of no use to me whatsoever??
Here it is:
And on the back: