Disassembly of Mamiya M645 PD Prism?

Picked up a used PD prism for the M645, and there is a boat-load of dust inside, as well as what looks like a strips of masking tape adhesive on one of the mirrors. I can't figure out how to open it up, and can't find anything on-line about doing so.

Anyone opened one up, and know how it's done?

The "masking tape adhesive" is quite likely the element separation that so many of these prisms suffer from.

Interesting. Here's a photo of the 'masking tape adhesive' -

Yes, I've done it. It was quite an adventure because a few screws on mine were permanently rusted in

It's been a while since I've done it. As far as I remember, the trickiest part was the finder release button. It's got a sticker that covers the screw in the center. You need to remove that screw and the button. You'll also need to carefully peel stickers from ASA dial and shutter speed dial to reveal screws that hold them. I think there are also a couple of screws behind the "Mamiya 645" decal.
That's about all. PM me if you have any more trouble.

I just did a search on the M645, and found an old thread that talked about the foam in the prism causing deterioration of the mirror silver. There was a picture, and it looks very similar to mine, so it looks like that's the problem, and I would assume the mirror is beyond cleaning or repair. So, while it's a little annoying when looking through, it really isn't a problem, so I think I'm going to leave well enough alone for now. Maybe one day when I've caught up with all the other projects on the list....