Which HP12 to buy?

[Don Shepherd]

I've got both a 19b and 19bii with the battery door on the side, and the door and the case sides are fine. Don't pay inflated prices on Ebay for 19b's with the battery door on the back. It's always a bit of a trick to install new batteries, but the cells do last a long time.

The alpha keyboard makes entering solver equations a breeze. Be aware, however, of what happens when you enter a solver formula that contains an error. You must fix the error before you exit the solver. If you exit the solver without fixing the error, your whole formula is not saved. No other solver (17b, 17bii, 27s) has this problem.