Greatest scientific pocket calculator in 1975?

[TomC]

Getting back to the original topics question:

Measure of 'greatness' is a somewhat subjective term and dependent on the times, so I will 'cast my vote' with the reasons why:

1975: The HP65

Why:
1. Pocket Size.
2. 'Nonvolatile' program storage via magnetic cards.
3. I owned one and 'wowed' my skeptical/laughing professors by outrunning our mainframe IBM1130.
4. Mitchell Feigenbaum (RIP) discovered his Constant given the HP65's unique capabilities.
5. I owned one (and spent a significant percentage of our disposable income to do so!).
(partial repetition intentional! )

..and I stil have it - it's waiting for the 'gummy wheel' repair.
Cheers,
TomC