Saw a Medusa today! Very interesting looking pin - I actually really liked the cabinet art on this one. It guess it was meant to have translucent flippers at the business end of the machine, and where those zipper flippers half-way up? The post between the flippers was able to be operated as a kicker, by the look of it.
Medusa is the hardest of all the Ballys of that era. Highly sought after Pinball. There were only a handful in the country, now there's quite a few coming in - which is great for collectors.
Translucent flippers are available from PBR, as is the rivetless targets. The "Shield of the Gods" makes the game look easier, but those side drainers are very common. Hardest and fastest Bally I've ever played. zippers are half way up.