The original 1955 356 blinker assemblies (like Gordon was mentioning) not only have the red SWF bulb/lens on the tip of the stalk, but also have ribs (for your pleasure) on the housing itself.
If anyone wants to see that original '55 blinker assembly, I have one in the display chest. Here are a couple of pics of a "back dated" early Beetle unit, which has the three ribs added, this time for my re-sale pleasure.
I made it to back date my 1965SC but sold that car.
http://img.photobucket.com/albums/v136/TeamEvil/blink5.jpg
http://img.photobucket.com/albums/v136/TeamEvil/blink2.jpg
http://img.photobucket.com/albums/v136/TeamEvil/blink7.jpg
Oh, for authenticity, the blinker housings were painted black on the early 356s. How horrible is THAT ? ! ? Just one more reason that I prefer the reproduction to the creepy original. WAY to post war Germany.