It says cos,then a little theta letter I think then say 0.99
https://youtu.be/U4n5vmpFtXw?t=796 The video starts at the label, also an interesting one to watch, I want to see him light up all the spectrum lights then put them into a splitter.
"cos .99": is that the power supplies way of saying dont feed square, triangle, or (most likely from its age) rheostat generated waves AC through it or you will damamage it? This looks rather old is that not an issue anymore? What would happen if you put square or rheostat waves into a modern cheap SMPS? Nothing? What about into a linear PS the good heavy ones from the pre 2000's(wall bugs) that were just two windings and minimal parts? I always keep those when I can find them, nice clean power for your projects, ordering one from china will set you back 40 bucks.