Had a quick look at the Pentax Serial Number database here:
Pentax Serial Number Database - PentaxForums.com
to look into how many cameras Pentax has been making.
Overall, the K-5 seems to have sold well for Pentax. But it looks like the older cameras like the K20D and K10D were pretty good sellers too.
K-5
Close-range of serial numbers:
4549461 (last serial) -
3453027 (first serial)
=======
1,096,434
K-x
Close-range of serial numbers:
3983874 (last serial) -
3418468 (first serial)
=======
565,406
K-7
Close-range of serial numbers:
3949211 (last serial) -
3374134 (first serial)
=======
575,077
K-20D
Close-range of serial numbers:
3844834 (last serial) -
2565783 (first serial)
=======
1,279,051
K-10D
Close-range of serial numbers:
3396226 (last serial) -
1909500 (first serial)
=======
1,486,726
The serial numbers do seem to be an OK guide to manufacturing volume, especially using the numbers in close sequence. If anything, the volumes indicated are likely to be very conservative, since this data source has a very small sample size.
The K-x serials also seem to go very, very high for only a few serials, so I've excluded those outliers. This may make the K-x numbers much more conservative than they really are, since (as I understand it), Pentax actually sold a LOT of K-x's.
It may be the same story with the K-20D. Some of the most recent serials in the database are much higher than the rest of the pack. They may also be typos.
Some things like the silver models of some cameras, or other special editions like the Grand Prix editions, seem to have a different serial number sequence, so they have not been included.
It's interesting to check these numbers against the
flickr Camera Finder totals for images shot with each of these cameras (data from today):
K10D - 11,276,882
K-x - 6,449,606
K-5 - 5,754,066
K20D - 5,340,342
K-7 - 3,860,101
The flickr data seems to generally tally with the serial database numbers, but the flickr data does, I think, confirm that the K-x data from the serial numbers database might be substantially understating how may K-x's were made.