What is the newest hardware/firmware version available in stores?

[DrD]

It's not all about the firmware, though. The color used on the key legends, have significantly improved the contrast, (and visibility!) on recent calculators. It' is very easy to tell, and you can see the obvious difference for yourself:

http://www.hpmuseum.org/forum/thread-6674.html

Older key legends may not even be visible, in some room lighting conditions. I don't know at what date this change was made, but it has been recently.

-Dale-