I've just picked up a Tek 485 for an unbeatable price; naturally it doesn't work due to the PSU "ticking". But that's boring until proven otherwise.
A surprise is that the photocopied manual is rather different to the manual from the usual places on the web. There's no contents pages, it is typewritten, and contains "pages 13-37 will appear in the permanent manual". The IC's datecodes are all 1972, and the s/n is B060xxx.
There's a little mould on the front panel, since the scope had been in an unheated seaside attic for a few years. On opening it up, at first glance the boards are pleasantly clean with one exception. The inter-board "5-way fingers" (and nothing else) have a brittle white encrustation, as shown in the pictures below.
What is the encrustation? Is there a better way of removing it than (gentle) suction, pulling the "fingers" out, and just brushing it off?