Just for grins, I ordered a new-in-blister-pack HP 6S Solar. I figured it would be fun to experiment with HP's cheapest calculator. From the Museum description, I expected a minimal-feature machine. I was surprised to find a calculator fully worth the USD $8 I paid (shipping included.)

Although algebraic, not RPN, this is a full-featured calculator that is more powerful than my favorite HP-45.

It offers the following advantages over the HP-45:

- LCD display and solar power - always on, never needs recharging.

- 42 keys instead of 35

- slim size really does fit in a shirt pocket

- animal-friendly non-leather protective case. (Well, it's a cheap brown plastic envelope made out of environmentally non-friendly oil, but let's be polite and say something nice about it.)

- instruction manual in English and French.

- 6 levels of "stack" using parentheses

- Base 2, 8, 10, and 16 arithmetic with bit-logic operations

- more trig functions

- Fraction mode, allowing entry of numbers like "four and one-third" (4 1/3) Fraction calculations stay in fractions until mixed with decimal numbers, then get converted. E.g. 1/3 + 1/3 = 2/3, but 1/3 + 0.25 = 0.5833333333.

- Fixed or Floating display

- single-digit correction "backspace" key for editing entry

There are a few drawbacks:

- No RPN. Whoops.

- Inexpensive manufacture; probably will last 5 years, not 50.

- Statistics are 1-dimensional, not 2-d

- Only one memory location "M", plus a stack-constant

- Manual is poor quality without the traditional intelligence and useful examples

- Keyboard layout is non-intuitive. Example: the four (shifted) functions for display modes (Fix, Flo, Sci, Eng) are not on adjacent keys. And the "shift" key is labeled "INV".

I have not had a chance to check accuracy. The manual claims internal 11-digit arithmetic, displayed as 10 digits. Mantissas go up to E+99. There are no thousands-group display symbols. The decimal point is easy to read. Mantissas are in a smaller font, so are clearly distinguished from the Radix. Like some non-HP calculators, fractions are shown with a very strange notation (because the display digits are 7-segment.) Keyboard feel is acceptable, at least for its price. Keys are rubbery, but make a positive click as they engage; I have not found any missed or doubled keystrokes.

Performance is lackluster. 2^5 = 32 takes about 2 seconds. There is no "OFF" key, common on solar calculators. I prefer solars that do have an off key; that allows the internal capacitor to charge up a bit, rather than running low. The calculator works OK in a darkened room with a single 60 watt lamp, but display contrast isn't great. In a sunlit room, display contrast is just fine.

All in all, a cute, semi-useful calculator with an HP brand name on it.