Anyone else keep an eye open for old tools? I picked up an OLD circular saw for $20

I have a soft spot for old tools. I picked up an OLD Porter Cable Model 528 Type B for $20. It is a little dirty and needs to be cleaned but, it works!

I am going to clean it up, might put a new blade on it and see what it does. It uses an 8 1/4" blade and says to only use blades rated for 7000 rpm. Has anyone ever been around one of these?

Looks like there is a plug to add oil (or something) to it. I am looking around online for an owners manual now.