Polishing a Micro Seiki RT 3000G Gunmetal platter

Would an orbital polishing tool be ok or is it better to use elbow grease?

Are you experienced with an orbital polisher?  If not, don't, in my opinion.

I may have misinterpreted the question.  but looks like you're getting a variety of anwers.  Good luck. --Jerry

Well, the OP didn't say what condition the platter is in, so it's hard to know what it needs.  What you recommended is on point if the platter is a little more worn than just lightly oxidized.

Lets rephrase the OP's inquiry.

I have recently received a Imported from Japan Micro Sieki BL 111 Turntable.

I am keen to keep it aesthetically appealing, as this Model has a used market value of between $4K - $6K.

I have a Platter which is in need of being returned to a Highly Polished Finish.

Can a method to achieve this be recommended? 

??? I have not revealed my experiences or competency levels to achieve this as a  finish by myself as the option.

That's a nice piece of gear ... follow @carlsbad2 's advice and you will be long-term happy