I have to say, I don't think much of your local jeweler! Wouldn't you think he could identify if the metal was plated or not by looking at it, especially as it is broken.
Gold testing equipment that you can use at home wouldn't cost much more than the price he asked.
Tom, the fact that there are maker's initials inside the ring doesn't necessarily mean it's made of solid gold. Electroplating was introduced in the 1840s. This involves the whole piece which is made of base metal, thinly coated with gold.
There are many antique rings that have been electroplated but because the ring has been passed down and therefore "old" then the gold plating should be pretty easy to detect.
Gold doesn't usually break in half. You will be able to tell if its solid gold by examining the metal carefully where it has broken, with a jewelers loupe or magnifying glass with at least 10x magnification. This is what you should be looking for...
Closely examine the ring and pay special attention to the wear points, especially the area around the break points. A change of color at these areas is especially evident if the piece of gold is electroplated over brass or copper.
You can find some gold facts here that you might find interesting.
There are are quite a few maker's especially in the UK with the initials GC so we would need to see a photo of the mark to determine the maker. However, if the ring is special to you, if it "sings" to you , then don't worry if the metal is solid gold or not. Get it repaired regardless. MANY important pieces are NOT made of gold.
