I just got a used Fender Starcaster S1 to compliment my existing Behringer strat. Upon inspecting it, I noticed that it has different backs on it's tuning machines. What are the differences between these besides appearance?
Inside them both you have a cog and a worm gear, which works as per this gif from Wikipedia:
Worm gears have a very useful property - they can cope with high tension without slipping.
The casing differences are purely cosmetic.
There are some easily noticeable differences:
Some differences are not so easily spotted, and may or may not apply: