A few months ago I was kindly given what looks like a late model 7 by a forum member. I can't find an obvious serial number
The rear of the meter movement is marked with what look like calibration dates (3/8/77 and 14/10/82) and there are 2 numbers on sticky labels, 814578 and 022369. The left of the scale has 'PART No 3284-144' and the right has '69847-7475'. There are 2 Exide 4.5V batteries fitted dated best before 1990, which I guess is some indication of when the meter went out of use. The 1.5V battery which is supposed to be in there seems to be missing - it looks as if it may have been a D cell. I have no idea of its history.
Paul