I think the device I use, very similar to the one shown in Robbie's picture, is a hand held progressive spring pressure indicator used for setting mechanical Relays or the like. Perhaps these are not used much these days as I'd imagine electronic switches replace the old fashioned leaf spring Relays . As Chris says, they may be expensive tools to purchase new but can be found at government 'surplus' sales and the like. Perhaps every telephone engineer had one in their tool kit?
Mine has the black 'crackle' finish paint on the all metal body and the maker's name CARPO ( made in France) on the dial and came in a small wooden box. It reads from 0- 175 grames. If I see another , whilst I scour the flea markets for useful items, I will surely liberate it.
PS ; a quick search on a classified adverts website and I found another, which goes from 0 - 50g, the seller says it is used for setting the springs in a typewriter.... for sale in its box for 15 euros! Another that will measure to 150g , the seller says it is for weighing letters, for 20 euros.
PPS; found at least 3 for sale on line ( in France) that will measure 0- 150 grams.... prices range from 15 to 30 euros plus postage. I'm sure you will find these locally.
Edited by Geoff Wooff, 04 August 2017 - 12:42 AM.