[68-69-70Nova SSL78]

I guess to get a double dash you would order any paint GM offered other than stock colors for the Nova. If it the color was offered in a Nova you would get that number paint code, Forest Green code 48, etc. Looking up camaro a while back the only color not offered to the nova but was offered to the camaro was Daytona Yellow and Hugger Orange. But you could have ordered other GM colors with the special paint/double dash. If that makes sense.