I've used Nisonger's in the past for magnetic gauges (Smith). They did mechanical AND cosmetic restoration. I just used Joel Levine for a pair of Veglias. He did a mechanical resto, but did not do anything cosmetically (paint, clean outside of bodies, etc...). I didn't explicitly ask for cosmetic restoration, but I was a bit surprised it wasn't done, considering the price. Veglias sit in a rubber binnacle anyways, so not that big a deal.
If you go with Joel, I'd consider explicitly asking for cosmetic restoration if that's part of what you're looking for.
Nisonger was a number of years ago, but it took about three weeks. Joel had my Veglias three weeks ago and turned them around in 4-5 days.