OK...Question about Irvin Caterpillar Club pins.
I've seen originals and repros of varying sizes. Anywhere from 3/4" to 1 1/4". The originals are pictured on some pretty reputable appearing sites and are not for sale so I wouldn't think they'd have any reason to try to pass something off as authentic that wasn't.
Did Irvin, in fact, make the pins in different sizes?

Mudge the researcher