That is a brand new 6" Yuasa rotary table for $100! Grab it before he comes to his senses.
If I were you, I would grab it, take it apart, put all the non-painted parts in an electrolytic bath and get the rust off. The surface will be pitted and cannot be helped but when it comes out of the bath it will be free of rust. Hit it with some Dawn and a maroon scotchbrite pad to get the black residue off, then use extra-fine gray scotchbrite to shine it up.
The table will still be as accurate as it was when it left the factory; no need to surface grind it unless you're looking to uber-accurize it, in which case you have to also scrape the mounting surfaces square and flat. Just as it comes from the factory, this table is very, very good.
I own this table and it is as smooth as silk. Almost no backlash and it is accurate. Yuasa made some of the finest tools and this one cost over $1200 when new. The internals should still be unused and is well worth the money.