Long life battery

I recently bought a Minolta SRT 101 i think the age of the camera is about 30 years old .I Was giving it the once over checking meter ,wind on , light seals etc .I went to change the battery for a 1.4v hearing aid job and found a original mercury cell in perfect condition and reading 1.35 volts on my meter .Mercury cells have been banned for at least 20 years in the UK so i am supposing it is at least that age .I have come across them before but they are usually in a sorry state but some still reading on my volt meter

I too found many dead or even leaking mercury cells, but a few still in working condition.
(But be sure they are true mercury ones, not depleted alkaline ones of the same 625 size that by accident show the same voltage.)

Just right now I found type 625 cells in a camera with a voltage of 1,33V that on checking out their manufacturer coding turned out to be Alkaline ones. Thus be careful as hinted at in my post above.