As the title of the post says... there are visible specs in the view finder. I've shot an image of the inside of the camera which should appear below.

It's a standard SLR setup with the mirror directly behind the lens. I've had a go at the mirror with a cotton bud but no luck. Probably somewhere else.
Has anyone cleaned these kind of cameras before? It's fully manual apart from a small light meter nothing is powered.
Thanks.
Alex