Hi Keith,
When my calculator crisis began last year, I desperately bought several 28s, 42s and a couple of 15cLE. As my crisis faded away, I realized that buying that way was ultimately a waste of money: it is better to pay now 650usd for a brand new 42s than buying 4-42s that go from almost garbage to a barely acceptable condition.
From that era:
One HP 28s 100 years American Mathematics edition: it looks like it was never used, but none of the keys in the last horizontal row work.
An HP 42s that looks like it was refurbished 50 times: it registers every key and passes self tests, but somehow when you press any key you don´t feel anything. It is like pressing a feathers pillow: the closest to feel just the air passing around your finger...
From my "original" units:
One dead 32sii (my third hp ever); it looks pretty nasty now, but in 5-6 years of life I guess it never saw any cleaning. It doesn´t power up (since 2004?), so I don´t find any reason to clean it now.
And phisically, I guess the worst is my first hp, an 11c. It looks just a bit less worn than your 12c, but I guess I dropped it at least once from a second floor, while in college. It powers up, but it doesn´t show both the dot and comma.
On the other hand, I proudly can tell you about my better units:
One boxed, brand new HP42s
One boxed, brand new HP 32s (50th Aniversary)
One boxed, brand new HP 32sii (USA made, 1989)
One sealed, brand new HP 32sii (Indonesia made)
One boxed, brand new HP 28s
One boxed, brand new HP 48gx
One boxed, brand new HP 27s
So I can say I´m happy now!!! And I hope I won´t need to buy any new calculator for the rest of my life :)
Edited: 25 Aug 2012, 5:41 p.m.