HP12-C quirks

[peter]

My first post!

After a quick browse on the forums, I could not find similar information and thought to post.

I recently purchased 4 HP 12C's, 2 made in 1984, 1 made in 1987, 1 made in 1988.

Looking more closely, I noticed that HP 12C's made in 1984 or before do not have the 871B logo, nor the "Complies with the limits for a Class B...." text.
This can be useful to note when shopping auction sites for pre 1985 calculators. An image is attached below as an example.

   

Serial # 2747A above, # 2434A below

On the 1987 as well as the two 1984 calculators, it looks as if some of the keys were (re)molded from an 11C or a 15C. Under a certain light you can see very faintly that some of the keys have different inscriptions - The images attached below attempt to get the right lighting to show the original e x below the i key (1987 calc).

Was it possible some of the keys were re-molded, or perhaps the manufacturing process shares the parts between calculators that might then leave an imprint?

   
   

Thanks!
Peter

[rprosperi]

(06-05-2016 07:47 AM)peter Wrote:  My first post!

After a quick browse on the forums, I could not find similar information and thought to post.

Thanks for posting and welcome to the Forum, or at least welcome to posting here.

If you look inside the battery compartments, you'll find the early models had different contact/spring designs from the later ones as well. As a Voyager fan, you'll find lots of detailed info can be found here: http://www.brouhaha.com/~eric/hpcalc/voy...iants.html.

Also, no 12C fan should miss Keith Midson's photos here: https://www.flickr.com/photos/keithmidso...7586986282

[Leonid]

(06-05-2016 07:47 AM)peter Wrote:  Was it possible some of the keys were re-molded, or perhaps the manufacturing process shares the parts between calculators that might then leave an imprint?

See "10C Series Versions" sections: http://www.hpmuseum.org/collect.htm#variations

[peter]

Fantastic! thank you Bob Prosperi and Leonid for those links, very interesting.

That blue version on Keith Midson's flickr is amazing, I will have to keep my eye out for one of those. I'm guessing they don't come around very often.

[striegel]

"On the 1987 as well as the two 1984 calculators, it looks as if some of the keys were (re)molded from an 11C or a 15C."

See my close-up photos of this same effect on an HP-12C from 1988.

There is a long and eloquent description of the reasons for this in the forum archives, written by Glynn in 2001.

[peter]

Striegel, fantastic pictures - those show the effect far better than mine. Thank you for the link to the explanation.

[rprosperi]

(06-05-2016 03:32 PM)peter Wrote:  That blue version on Keith Midson's flickr is amazing, I will have to keep my eye out for one of those. I'm guessing they don't come around very often.

I'm not sure it's a matter of "they" coming around often, it could be just that one... or maybe a handful. These were made during early mold tests using various colors (as well as clear cases), and a few made it into the wild via HP Engineers that geeked like the rest of us over these odd beauties.