Double Die Reverse Swiss Franc Gold
 

I have a 1930-B swiss 20 francs gold coin - Helvetia. I had it graded...and it came back ms65 Double Die Reverse. It appears....Double Die Reverse mint error coins are worth alot more than regular graded coin...obviously...but I am having trouble finding an older Swiss coin which is "double die reverse" mint error.....

Anyone have an thoughts on this type of coin? Any opinions appreciated.