Classification of Gillette DE razors

Hello friends,

Please forgive me if this has been covered but I have not seen a thread on this topic.

I searched for "Gillette Safety Razors" on eBay and came up with 1200+ hits. I'd like to shop for one but I don't know enough about the various types to make an informed decision.

I realize the quality was there (at least originally) and individual preferences are all over the map. But what I'd like to know is what are Gillette's grades from top to bottom?

Also, should I restrict myself to Made in the USA or are razors from some of the other countries worth a look?

Thanks in advance,

Musikmann