A while back, I got ahold of a Tamron CF Tele-Macro 80-210mm f/3.8-4. It was my first experience with a Tamron Adaptall-2 lens.
I like the lens. The bokeh's a little harsh, but it's very sharp, built like a tank, and can focus down to just under a meter. However: It came with a plain-Jane Pentax K adaptor.
Remedial Adaptall information follows: Tamron's Adaptall (and Adaptall2) lenses have adaptors which let you use the same lens with a variety of different camera mounts. I have another one of these lenses (28mm/2.8) which came with a Fujica adaptor. Pop that off, put on the Pentax adaptor, and I'm shooting pictures immediately. Very handy.
However: Not all Pentax adaptors are made the same! The adaptor that came with the zoom lens doesn't allow any sort of automatic metering, since it was designed for all-manual cameras.
The point here is that there are two different Pentax K-mount Adaptall mounts, and I ended up with the less-desirable one. There's another mount that is compatible with Pentax A-series mounts, allowing all the happy automatic metering a boy could dream of.
The plain-ol'-K-mount variety is labeled 'P/K,' and is model number 02C. The K-A variety is labeled 'P/KA' and has some extra electrical contacts around the edge. It is model number 63C. It also features an A-position lock, that works much like the lock button on normal Pentax lenses with an A setting on the aperture ring. It's a black button on the adaptor, and is located in a somewhat inconvenient place (on the bottom, on the opposite side from the lens release), and is difficult to use (you have to use one hand to press the button and another to turn the aperture ring) but we like it anyway. We guess.
With this adaptor in place, the Pentax *ist DS (and probably D, D2, DL, and *ist film camera as well) will meter as well as the camera can with any other A-series lens. Which is pretty well.
The MakerNote in the picture's EXIF data will say that the lens is an A-type lens, with a focal length of 0.0mm. It'd be nice if there were a way to have the lenses identified, but I guess Pentax can't design their cameras to read the mind of every lens attached to them.
As with other Adaptall mounts, you should make sure the lens aperture is set to wide open (the smallest number) before installing the mount. When it comes time to remove the mount, you have to make sure the aperture is not set to AE, or the mount won't come off. But you already set it to the smallest aperture anyway, didn't you?
Some of this information comes from a Tamron Adaptall-2 FAQ which I recently found. And the FAQ is wrong when it comes to the Pentax *ist DS (and, I assume, the other *ist cameras). The chart states that the P/K adaptor allows one to use aperture priority AE with the lens, but, in the case of the Pentax digital SLRs, this isn't true.
See also my article about manual lenses for more details.