Why did you peel off the battery?
I've noticed many electronics from back then, when the remote controls and pocket calculators used to be a PCB black blob instead of a chip with soldered terminals, they tend to preserve very well the batteries.
I have a few thermometers, a remote control from a former AC kept because of it's very good accuracy as a clock+thermometer, a pocket calculator, the clock inside an old Samsung boom-box, all have a PCB black blob IC, and they run for 5-10 years, maybe more, with the same battery.
I wonder if such PCB-blob chips somehow acts as an energy harvester from the surrounding EM fields (unintended, only as a side effect of that technology), so they recharge the battery. So far I have had at least two batteries that lasted longer inside the clock of a digital radio than the other two batteries from the same package that were sited as NOS on a shelf. It's a mystery.
Anybody knows what technology was that, during the 70s-90s, when the IC used to be a black blob on the PCB for many consumer devices like clocks/thermometers/pocket calculators? It was CMOS, or something else, and what size?