I have used Flitz on my nickel plated phonograph parts and nickel horns for years with exceedingly good results. You can get it at any Ace Hardware store and other hardware stores and online. The nickel plated parts on this AB you found appear to be in generally very good condition. I used Flitz on my nickeled and polished Columbia Eagle in the picture above.Zenger wrote:I'd also be grateful for any tips anyone might have on cleaning up the bedplate and horn.
Regarding the governor, I agree with Jerry that you should consider having it serviced or take it apart yourself and replace the 3 springs and check the weights. Harbor Freight (among others) sells petite digital scales that can be useful for checking the weight of small parts which is extremely useful with governor weights.
Doug