Call The Brass Center in NYC - they do a great job and are surprisingly not as expensive as you may think. Here is their link: http://www.thebrasscenter.com/

What was the original finish, or what finish are you seeking? (nickel?)

I really like the uncoated brass -- it'll be beautiful if you just polish it up with some brass cleaner, and give it a coat of Turtle Wax.

Are you sure it wasn't just brass hardware to begin with? Cleaning up the brass and removing whatever paint is on it is a DIY type of job, but plating or replating it with a different type of metal is not. Other than the paint around the edges, it has some nice patina on it. I would consider just removing the paint and leaving them as is. If you still want plate them in nickel (or whatever) you could try custom hardware places like E.R.Butler or P.E.Guerin but they aren't going to be cheap.

If you want to leave the finish brass and want an earth-friendly way to clean it... I used ketchup to clean the vintage brass knobs on a dresser I inherited. You just take the hardware off and let it soak in the ketchup for a few-24hours. wipe the ketchup off with a clean, soft cloth. Should be pretty shiny after that but if you want to protect the shine and keep it from tarnishing over time I would follow mschatelaine's suggestion of giving it a coat of some kind of wax. Hope that helps if you decide to go that route! Unfortunately I do not know of any replating companies that I can suggest!

Try some brass polish first - you may like how they come out!

Ketchup!??! I've never heard anything like this before...what is the active ingredient that cleans the tarnish?...interesting!

wuerin-- it might be salt. There was another posting--I think on AT--that explained how to strip paint from metal hardware by leaving in boiling water with salt for a few minutes. I tried this and it worked very well.

tomato sauce I would say is the active ingredient. Highly acidic. Have you ever noticed your stainless steel pots after making bolognese sauce :-)

http://www.ehow.com/about_4603979_copper-brass-cleaner.html

Coca-Cola is another option!

I was a NYC designer about 5 years ago.
My source for this kind of project was:
American Electroplating Co Inc
342 Lincoln Ave, Hawthorne, NJ 07506-1232
Contact Phone: (973) 427-2300

I have not called to see if they are doing small jobs but I used to call them and mail them a box of hardware, they would clean and refinish - then mail them back, sooo easy and my clients were always impressed. Owner was Dave, nice guy. Hope they are still around, worth a call. Tell them Lynne from Ville says hello!
Good luck, Lynne www.designbyphoto.com

And if by chance you want them darkened, say going for a 'bronzed' look, Google for 'metal darkening liquid'. Though, honestly, I like the ideas above to keep them as a brass finish... they're really beautiful hardware.

BTW, metal darkening is what I use to unite disparate metal finishes in the house, I've brushed it onto lamp bases, dipped doorknobs, hinges, hardware. The mismatched hardware was driving me a bit nuts and I opted to try to match it all (on my own) rather than buy all new or pay someone to dip & re-plate. I figured if it didn't work, I'd pay someone or buy all new, but so far it's worked well on everything I've tried.

The Navy has a secret chemical compound for polishing brass. Bug Juice, aka concentrated soft drink mix, aka kool-aid.

Mix unsweetened kool-aid, preferably a 'red' flavor, with only 1/4 of the prescribed water. Let the parts soak in this mixture for an hour or so then rinse and buff the heck out of them. Repeat if necessary.

Caution: wear gloves or your hands will be red/pink for a week.