Marks visible in K2 viewfinder

I recently bought a K2 film camera as part of a package and it has a couple of problems. The first is the typical very stiff ISO dial - I need to have a look round the web to see if I can find any tutorials to loosen that up. The second is something I haven't seen before: there are some marks visible in the viewfinder. The marks are only visible when there's a lens on the camera (doesn't matter which lens) and there's nothing visible on the mirror or on the focusing screen. When there's no lens on the camera the marks are not visible.

They don't prevent the camera from being used but are a bit annoying as everything seen through them appears unclear, but if anyone has an idea of what they might be or how they might be removed then it would be nice to know. My guess is some kind of degradation within the prism.

I managed to take this shot using the K-3 and DA 35mm. I've used software to make the marks stand out more.

Many thanks to anyone who can shed any light on this.


Strange marks visible in the viewfinder of a Pentax K2 by Jonathan MacDonald, on Flickr

The images remind me of a mirror where the silvering has degraded. Is it possible that the pentaprism needs to be re-silvered?

Michael

Others have suggested de-silvering. It's not a problem I've come across before so I don't know what it looks like.

I have just come across this https://www.pentaxforums.com/forums/8-pentax-film-slr-discussion/318625-pentax-k... Any use??

Thanks, that does look similar to what I see in this copy of the K2.