Thanks David

About a year and a half old (second copy, as first was soft).
Not used much as I prefer ultra-wide and distorted, or macro, or out around 300mm. So it seems a bit extravagant to keep it.
Very good condition, no marks, boxed, but I've lost the hood.

I'll get back up here with pictures and a price, but in the mean-time, feel free to make me an offer or suggest a suitable price.

For anyone wondering (as i have for years) whether a £30-£40 mirror lens can be any good? I can confirm that it can!
It takes some handling, being fixed f8, totally manual and incredibly sensitive to movement, and focus, and where the light is. But in the right conditions it can produce really interesting and perfectly acceptable results. It's a real eye-opener looking at the world through 500mm. I spent a really enjoyable hour with a beer, sat on the Hoe in Plymouth one bright evening just pointing it at stuff.
I went up there specifically to shoot the crane over the roof tops (hoping for a sunset, didn't happen) and for this it really excelled.






All these images were fine at high res too. Need more work than a good lens obviously, but perfectly usable up to about 10x8 I would think.

I might have a go.
Some tips I have discovered in the past:
1. make the hole very small, clean and sharp (no burrs)
2. try making a telephoto by mounting the pinhole on the end of a tube (IRC, I got '200mm' with a toilet roll)
3. Use foil for the 'lens'. slightly thicker foil from wine bottle or drinks can aluminium, can be polished after creating the hole, to get a smooth, thin, regular hole.
4. Use an old digi camera not your latest K5 - you're likely to get dust on the sensor.
5. You can use the lens blank from the camera body packaging, drill biggish hole in it, then tape your prepared foil over the hole. But just taping a piece of card there will do to mount the pinhole.
6. Forget all the above and mock up a really bad photo in PhotoShop

Excellent, incisive, informative! Rude not to go and buy some new windows now

I should stress that the JPEGs from the K5 are fab.
When processing the RAW file I have much more trouble getting past their standard than I used to.
Th K5 RAWs have less oomph innitially, so need more time with the saturation etc. But the ability to do almost anything with them and get away with it, just keeps putting a smile on my face - like this

Ah, yes of course, that'll be the clincher in this - the K10D to K20D comparison. Thanks Glyn.

I'm really happy with the K5, no excuses any more!
However I have noticed the images aren't as punchy as my lovely old K10D.
Is this just a characteristic? or is it connected with the increase in sensor resolution?
Is it possible that the lens can only pass a certain amount of 'information' and eking-out that info into a bigger file reduces the concentration? Just a wild guess...

I started with the K10D, then bought a K-x which has almost magical high ISO performance in comparison. Then I bought a K7 for a wedding. All the indoor shots with the K7 were disappointing, I used the K-x for anything difficult. The K10 was with me but was set up with an old Metz and didn't get a look-in.
I did a comparison of ISO between these 3 and the K10D was actually better than the K7 at 1600 astonishingly, however the K7 has nicer quality grain.

I now have the K5 and it totally out-performs all of them, albeit with less 'pop' from the raw files. They always need beefing up, unless I use the JPEG. The K10D always produced beautiful images in good light.

If I had the K5 for that wedding, I would have had far more 'keepers' indoors. (make-up, children, atmospheric preparation shots etc.)

Try and lay your hands on a K5; it will not only be miles better in low light, but will help you rescue difficult exposures, and/or allow you to underexpose deliberately to save the dresses. The K7 will be frustrating anywhere but outdoors, even with a flash, you'll need high ISO to light the room nicely.
The K5 is so much more forgiving, it'll take away half the stress right there. The grain is also nice like the K7, so you can relax if they do get a bit grainy.
I can't get too worked up about having to use a Canon, fast-focusing might be a nice bonus, but the K5 + K7 combo will feel like everything you need