If the seller kept a copy of the e-mail disclosing the serial no. Then this can be used to show the information predates the insurance claim...

Whilst Bernards message is too let for the OP, he makes a valid point. I would never use acetone to clean near unknown plastics. iso-propanol (also known as 2-propanol propan-2-ol...) is a much better choice - being fully miscible with both water & most hydrocarbons - without the tendency to eat through plastics.

We use acetone in the lab where I work, and I have had many pens, etc attacked by just residual amounts on gloves etc.

Rather than the inconsistent lighting, it's the apparent angle of view that makes the false sky obvious as a replacement. The view of the castle is clearly looking down, so I'd expect to see distant landscape at the base of the sky area.

As far as Cheating goes, it can only be cheating if you try and pass it off as something it's not.

I generally find it more fun to do my 'cheating' in camera, but see no reason to refrain from post processing to remove distractions (reflections, sensor muck, even background objects) where this couldn't be done in camera.

I like to think so, but I in truth I'm probably just a cheapskate. In any even the original Idea wasn't mine so I cant claim the glory here.

I couldn't make it for the meet, (It's a good 5 hours from home) but I did manage to visit today, spending my lunch hour there on the long way back from Knockhill.

What a fantastic place!

It's getting a little late in the year for dragonflies but there were still some willing to pose for me.

This one seemed particularly co-operative, and at one point landed within inches of my shoulder.

The bargain option is to use welding glass (usually under £5) though you do have to arrange a mount (sticking a cokin adapter for your lens size on works well) and they have a strong green colour cast but this can be corrected. Some apparently can have flaws distorting the images but I've not seen this in any of the ones I've tried.

Welding glass comes in a range of shades, (from 6-15 but mainly found in 10-13) but any of the common ones should give a useful exposure increase. My shade 13 has enabled me to photograph the sun at 1/500s (f16 with a 200mm lens) even showing sun spots.

Actually reading all the way through it, it shows that the filter works quite well unless pushed to extremes. No variable density filter will work well on super wide angle shots. The drop in sharpness on the telephoto shots does look disappointing, but bare in mind they are 100% crops!

I've not played with mine yet (except off the camera) but it certainly seems worth more than I paid for it

Found this which might help:
How to convert Yashica/Contax to M42 mount

I assume you mean the Contax/Yashica (registration distance 45.5mm) rather than the rarer Yashica Pentamatic, Pentamatic II (registration distance 43mm).

As others have already said infinity is likely to be a problem unless the CY mount fits inside a PK (~0.04mm is not much to play with but even that's better than -2.6mm...)

It would be possible to get the mounts on the lenses changed, or to convert a teleconverter but it's unlikely to be worth the effort.

For macro work several bellows take interchangeable lens mounts allowing a vast range of lenses/bodies to be connected together in just about any combination. I believe BPM also do a shorter connector for these mounts that does away with the need for the bellows (but still gives effectively an extension tube).

T2 (& adaptal 2) adapters are also very common, and I've also used a m39/PK adapter (for enlarger lenses) though that was with bellows/extension (My helicoid doesn't go out far enough to reach infinity focus with one of them). Various medium format adapters are also available.

The only adapter with a glass element I've seen is to mount Nikon lenses - but my only Nikor is M39 anyway

The trouble with this is when you come to use a lens on multiple formats (My M50s get used on a dSLR now but all have been designed for full 35mm SLRs with a different FOV). Focal length makes much more sense.

Mind you focal length becomes a poor measure with fish-eye lenses, once you leave the rectilinear designs, focal length doesn't give much of a clue to field of view.
There are 4 basic designs (equidistant, equisolid, orthographic & sterographic) for fish-eye lenses with quite different mapping functions. Some theoretically give about twice the FOV of others at the same focal length/sensor size. To confuse matters further real lenses are usually a mixture of several basic designs, and FOV does not always vary linearly with crop factor.