That's most definitely not a Topaz. That's more like a Jasper or an Aventurine.
I'm pretty certain that this doesn't have much value and the value it does have is in the metal (if it's not a base metal) and its likeability. How much does the vendor want for it?
Just for info - Topaz is a "cheap" stone. You can buy it for next to nothing if you shop around.