It's one of those cheap things you get from this or that place for free, usually with a logo or something printed on it. It probably costs about $0.25 to make, package, and ship one to the US from China. Add, subtract, multiply, divide, square root, a basic memory function--capability which used to cost hundreds of dollars, but thanks to the miracle of integrated circuits these things are cheap enough to give away, and throw away when they stop working. Many of them incorporate a small solar cell, on the theory that if there's enough light to use a calculator by, there's enough light to power the thing.
This one has a clear plastic case, and what caught my attention was how neat that would have been back in the old TI-99 days. I saw the solar cell and bceame a bit curious about how the wires ran from it.
...only I couldn't see any wires attached to it. And further inspection revealed that it had a battery, mostly hidden by the "Made in China" sticker. (I hardly think the placement was entirely accidental.)
"Now, wait just a cotton-picking minute," you may say. I did. "What's the point of putting a solar cell in the thing if you're not going to connect it to anything?"
It certainly didn't make any sense to me to have a solar calculator with no connections to the solar cell and a battery. The whole point of including the solar cell is supposed to be so that the calculator is usable for a good long time, as you're not relying on a battery.
"It must be a fake solar cell," I concluded, though just why someone would bother putting a fake solar cell in a calculator was too stupid a question for me to consider. I got my toolkit out and disassembled the thing, intending to remove the fake solar cell, just to reassure myself that there wasn't something I was missing. Six screws and the case came apart, and I pulled the fake solar cell out.
The fake solar cell has printing on the back, and a part number--HP-2510DS--and terminal pads.
"No f-ing way," I said. I got my multimeter out, hooked leads to the terminal pads, shined a bright light on it, and got a reading of 2.5 f-ing volts. It's a real solar cell!
A real solar cell, and it's not connected to anything, and there's a replaceable battery on the back of the circuit board.
Yeah, I need the picture of Kyon again:
So here's what I think: I think the thing was originally meant to be a solar calculator, but for some reason it didn't work well on room light; by that time, though, the case had been designed and made and was in production, so they added the battery and skipped wiring the solar cell, and that came out as a wash in production costs.
This explanation keeps my brain from imploding.