Hey Glort,
On the subject of back-feeding an old mechanical meter - Have you tried it?
I was fortunate a while back to get a few meters of various ages and vintage - all scrapped, with a bit of cosmetic/closure/lense damage mostly ... They were all working reasonably well, but needed calibration of course... While I was playing with them, I noticed an interesting little mechanism on the worm wheel that drove the counter/display digits. It was an anti-runback ratchet and pawl - when backfeeding these meters, they would spin a few revs in reverse and then hit the stop... All but one out of about 20 or so had this mechanism in place, deep in the innards of the meter, not easy to get at without removing covers and fascia... The one that didnt have the ratchet, had been tampered with, by the looks of it, so I reckon the ratchet mech must probably be pretty standard... And judging by the ages of these things, been around for quite a while too...
Just saying....
Cheers
Ed