One extra unusual thing about this particular calculator, Texas Instruments didn’t even bother to etch a serial number on the back. And these calculators didn’t use stickers for the serial number, they melted the numbers right into the plastic. But mine, blank.

The only thing they put on the back of mine is a big capital R above the serial number field. It took me a bit of research to find out what that means.

It’s a refurbished unit straight from Texas Instruments.