Ultraman Masks: A, B, and C Types

Type A Mask
Episodes 1-13
Latex on FRP (don't know what that is, unfortunately)
The first mask. Not very pretty. The mouth portion is designed to move. On some occasions, his boot tips point slightly upwards. Eyes slant upwards considerably more than they do in later versions. Overall, the effect looks like he was sleeping on his face all night and just woke up.

Very little muscular definition on the rest of the suit (it's the tall and lanky Satoshi Furuya inside the costume).

Type B Mask
Episodes 14-29
FRP
A simpler, more elegantly designed mask, which lacks the crumpled look of the original. Easily distinguished by the small mouth.

Slightly more muscular definition on the rest of the suit than on the previous version.

Type C Mask
Episodes 30-39
FRP
The mask with a relatively wide mouth. I think it's safe to say that his mouth set the standard for future Ultraman suits. The mouth of Ultraman Dyna is based on this C Mask.

The rest of the suit is the beefiest of all Ultraman suits, with the most prominent pecs.