: Hi, this sounds new and very funny indeed. Can you pls. provide
: some more information on the topic?
: Thanks anyway.

: Fabrizio

Hi
No problem, this is how I see it (and I welcome all corrections and additions)

There are the straight 5100s.
These are the 510. 500, 501, 502, 503, 543 (AMI), 511 and 523 (both Cortinas). That's Easy. 7 models.

Next, there are all the variants that do not employ the 24-hr subdial at 12 o'clock, which is a feature of the 5100 movement.

These variants are
510. 403 (both Silverstone and plain-dialled), 513 (Cortina), the Audi Sport (no ref). 4 models

Most of these contain 5100 movements (beat rate 28,800). I say most, because there are some examples that seem to have 5012s, but there seems to be no rhyme or reason as to which (and some may be put-togethers). As the 5100 feaures the 24-hr subdial these models simplify the movement, or just chose not to employ a hand or sub-dial in that location, leaving plain dial over the top.

And lastly, there is the odd-ball, the 510.500/12 (genuine code - see OtD). This is the plain steel version of the 510.500, externally identical, but it utilises the 5012 movement, which can be seen on the movement identifier badge inside the caseback. This movement is the slower beating version of the 5100 (21,600 not 28,800). The odd thing is that although it says it is a 5012, and has a model code to match, it has the 24-hr sub-dial, a feature that the movement is supposed to lack (in traditional wisdom).

This additional feature on the slower movement is to be found nowhere else to my knowledge (and I am aware of over 60 different manufacturers using all of the 5100 movement family variants, the 5100, 5012, 5270, 5250, 5190 and 5195).

So Heuer (actually most 510.500/12s I have seen are Tag Heuer) must have gone to significant effort or cost to add this feature onto the 5012 in order to make it mimic the 5100, when all along they had been producing at least 4 models that could have used the 5012 as it was.

It seems nuts, but I am sure it is related to the desperate parts-bin manufacturing during those most difficult years.