Oldest Working AA Battery?

[BogStandard]

Back in around 1983 I bought a calculator for my daughter as she was starting Secondary School.
I still have it in a draw but it has rarely been used in the past 40 years. Yesterday I turned it on a couple of times and it powered up although only for a short while. I had no recollection of ever changing the batteries so opened the battery compartment and saw they were the original batteries dated 83-06. They had not leaked in all this time although the contacts look a little corroded. I spun the batteries in-situ to freshen the contact points and it worked!
I have attempted to attach images but my earlier failed trial attempts mean I have exceeded an 8Mb quota.
The batteries are branded Casio in white lettering on a blue background.

Regards…

[DA74254]

Yep. I havwe tha same. A Casio Fx 82, which I bought for my final year at ground school (9th year in Norway). This was the school year '83/84, so bought some time in the autumn of 1983.
Still functional with the original blue batteries with white Casio print.

Unbelievable quality on those batteries. Mine isn't even corroded, and just works :-)

[Garth Wilson]

This AA battery is still at 1.51V, without a load.  I didn't try it with a load.  I don't see a date code on it.  Maybe it was made before the calendar was invented, LOL.  The rectangular 30V battery is dead, but there's no hint of leakage.

[Sylvain Cote]

Wow!
I have not seen that Eveready battery color in a long time.
From Quora

Quote:Eveready batteries, unless they are marked “alkaline,” are carbon-zinc piles. You can use one to exhaustion, and then switch it off. After about a day the depolarization process will restore the battery to full strength. Hence, “nine lives.” Eventually the depolarizer will be used up, rendering the battery drained for the last time.

[xerxes]

(09-08-2024 03:02 PM)BogStandard Wrote:  The batteries are branded Casio in white lettering on a blue background.

I've the same batteries in my FX-180P bought in 1980.