HP certainly had painted key labels on HP-12Cs, 15Cs,
and 16Cs.
I have seen HP-15Cs with HP-12C key labels shaded
beneath the 15C labels, also 16Cs with 15C _and_ 12C
labels below the 16C labels. Dave has some images of
these on this very web site! More recently, it was
pointed out to me that some 12Cs have 15C labels
below the 12C key labels. I do not know of other
combinations, and suspect that all 10Cs and 11Cs,
as well as early 15Cs and 16Cs had moulded key labels,
not painted ones.
What really interests me is what the technology was
behind the key labelling at the time when these
"interchangeable" keys were produced. Did HP make
one huge batch of keys at a time, sometimes 12C,
sometimes 15C, then paint the others over them?
But in that case, why vary the basic keys, sometimes
12C and sometimes 15C? Or was a technique used such
that traces of the previous label were left in the
machine when a new design was used? In that case,
someoene, somewhere, should have a 12C or a 15C
with signs of 16C key labels below them.
Does anyone have such a 12C or 15C?
Thanks, tom, for reminding us of this interesting bit
of history.
Wlodek