I don't know a good way to be certain that the entire frame is chromed, but I believe that if the frame is painted then there had to be at least some roughness to the chrome. Sometimes this is minimal and the bare chrome still looks beautiful. Other times it looks like someone took sandpaper to your chrome frame. Other than reputation of a particular frame I don't know if there is a reliable way to know which of these you'd have even if you did know it was all chrome.