I agree with Linnea, that it's the rim where the plating may wear off, but it's very unlikely that the rim would wear before the center portion of the tray which gets the most use.
And I have only very very rarely seen silver plated over brass,and all that was made in India......more likely it's plated over nickle silver or copper.
Try cleaning it using a liquid polish like International silver polish and a very soft tooth brush.
If a silver tray wears it's usually in the center where you put the coffee pot that will wear away first.
I don,t recommend using a citric acid based cleaner on anything but that which you KNOW is copper.....and not always then....it doesn't leave the nice luster that a solvent based cleaner does.

What's the marki on the back of the tray? EPNS? Or "silver on copper"?
Linda C

I have a large S/P lazy susan (from the 50's or 60's?) that's treated with some type of anti-tarnish coating & polish doesn't have any effect on it. While the piece doesn't tarnish, it doesn't have the luster of uncoated plate & doesn't clean up as well; in fact, it always looks like it needs a light polish! This is a high quality, copper based piece & I didn't have an inkling that there was any coating on it when I bought it. I suppose it's possible that it was produced with some areas left uncoated & they would definitely tarnish. I believe it has a brand logo that subtly implies that it has this questionable attribute.

Thank you everyone for your responses! The tray, 2 pots and sugar/creamer were all a gift about 30 years ago. I do not know the maker but will look next time I'm there in a few weeks. I do not feel the plating on the rim alone has all been rubbed off at it would be uneven - some plate left on in certain areas. It's not flat, a rolled edge; which is why I felt it may be of a different metal under the plate (so it could be sodered onto the tray). The leg base for one of the coffee pots is affected the same way. Mother-in-law has been very gentle and good to this set all these years. I will look for International Silver polish, and try a brass and/or copper cleaner on a section underside. I may try contacting the company who plated it, if they are still in business. This is not a cheap quality set and I would hate to do it more harm! Again, thank you!!

Why not get it replated?

Because you destroy any antique value if you replate a piece....unless the piece is in VERY bad shape....and it's very expensive....close to $1.00 a square inch.
Twila....could that piece possibly be "old sheffield" plate??
If it is that's a whole nother thing, as they say!
Old sheffield is indeed over copper but not electroplated but rather rolled and the copper coated with pure silver and the trim and decorations are often sterling or plated in a different way.
There also was some "stuff" that was chrome plated over copper and the trim on themw as a white metal...nickle silver.
Find out how it's marked.
Linda C