Your block on the right shows the Antique "C". Where the ends of the "C" almost close on each other. The regular font is smaller, and the end of the letter "C" extend almost straight out. The Antique text is also larger than the regular text.
From what I can see, you only have one stamp with the regular "C". That is the middle stamp on the right side of the block of six.
To answer your next question, yes, the overprints of the same fonts come in different sizes.
I have some Nicaragua stamps that were described as some with an Antique font 'C'. I am totally lost as to differentiate between a regular and an Antique Font C, could someone help me out. see attachment.
re: Antique Font 'C'
Your block on the right shows the Antique "C". Where the ends of the "C" almost close on each other. The regular font is smaller, and the end of the letter "C" extend almost straight out. The Antique text is also larger than the regular text.
From what I can see, you only have one stamp with the regular "C". That is the middle stamp on the right side of the block of six.
To answer your next question, yes, the overprints of the same fonts come in different sizes.