I find no problem with the K1 at ISO800, which is where it normally is these days. As to noise, one of the best removers I have found is in Faststone image viewer - shortcut to find it is Ctrl + J. There is a lot of control over what happens and it's very effective.

Lots of them on Ebay presently for less than a tenner.

Priceless !!!

Definitely worth purchasing this one. Congratulations on your success Bill.

That's a mighty expensive lens to be mucking about around the front element with the edge of another lens! Now try blu tacking the coin to the end of the slider so you can move that in and out rather than the huge unwieldy camera ensemble.

Thank you everyone for your very kind comments. (Thank goodness my location is included with my avatar !).

See if I've got this right. I follow the way you discover the total focus distance and divvy it up according the the number of shots you will use but you are dealing with (a) a linear focusing method and (b) a rotary one. The pointer is fixed to something mounted on the linear method yet the scale is rotary. Are you moving the slider, using the focus knob or are you twisting the focus ring of the lens, which rotates the entire protractor scale against the fixed needle?

Don't let the lack of fancy, expensive lenses put you off FF (expensive enough on its own!). I can't afford them either but I have a great collection of A series, FA series and manual M42s - some of which will give the four figure Self Destruct Motorised things a good run for their money - and they are dirt cheap.

Methinks the gentleman doth protest too much.

I made some space for a lot of kit this afternoon. Two tripods - one for the coin Blutacked onto the end of a BPM focus slider and one for the camera and it's accoutrements.
Attached to the K5 was a BPM bellows half extended sitting on top of a heavy cast iron Pentax focus slider (hefty great thing - I've never found another). A Takumar f4 200mm was attached to the bellows and a Takumar 28mm was reversed onto the end of it. Lighting was from an anglepoise lamp hard up against the target coin which was a brand new, shiny copper plated 2p. I couldn't find a penny so, as this is about the size of an old halfpenny, I deemed it a fair substitute. The engraver's initials were just below the Queen's bust, as normal. Shutter release was after mirror lock up and by IR remote.
The main problem at that magnification was navigating to find the target. After that focusing was done via the target's slider. Even with a shiny new coin that looks mirror finished, the surface texture and bits of this and that on it (or in it) are quite surprising. Anyway, here is my result. Looks like there is some shutter shake even with all the cast iron work put there to prevent it !