Is it really a Hewlett Packard?
There are two scientific calculators recently produced that, I'm afraid, fall into the cheap, plasticky category. They are the HP300s+ and the HP10s+.
The question is, are they really Hewlett Packard machines at all?
They are not. They are in fact Casios that have been rebadged to look like HP machines.
Want proof? Watch this video with the HP10s+ showing its real colours. If you press the MODE key four times you get to the menu where you can alter display settings. There is an undocumented function in this menu where, if you press '2', you get to the contrast setting. This is not mentioned in the manual and, indeed, it has no effect, but look at what you get on screen when you press '2'.
One good thing about this little machine is that I didn't even have to put a battery in it. The solar panel above the screen provides enough power to run the calculator as long as there's enough light around.