That is a beautiful old tray, but not really as old as it looks. The original tray was a rectangular one with this picture. It was produced in 1923 and again in 1924 with a more cropped picture and different border. Different shaped trays with the same picture were reproduced in the 1970's and 1980's.
Your tray was made in the '70's. It was part of a promotion to "recapture the 20's on trays for Coca-Cola" campaign. There was a set of three, each selling for $1. This tray, in perfect condition, is worth $10 today. The one from the 80's, which was round instead of oval, is only worth $5.
The thing to keep in mind, however, is that what you have is an official licensed Coke product. Depending on collectors, demand and where you sell it, the price can vary. I have seen many items sold for very high prices on eBay, where the buyer must beware. Most people who sell these items provide little information and leave the decision up to the buyer. That's not always the best way to do things, but you see it happen at flea markets all the time.
Anyway, I hope that helps. Even though the value of your tray isn't that much, it still looks like a nice piece and you can always "play dumb" to friends saying it is a nice old piece from the house. Hee hee... Hope that helps and hope you are not too disappointed!