I don't know if I would call it educating, but I do have a marble or 2.
I have a lot that have become less desireable with age. I have one that was beaten unmercefly with the "ugly" stick. Knockout drop dead gorgeous till about 10 inches..... Now, she looks like an almost sub par Marble. Had crazy Marbling at a few months old, now some may not even believe it's the same fish.
You VERY rarely see Marbles over 18 inches. I believe it's cause they look like normal Motoros.
Seems to me most are allready at thier prime or on the decline at 12 inches.
Maybe it's just me. Maybe I have bad luck, or bad water, or bad eyes, or a newfound bad attitude towards them.......

I'm calling it the thousands of dollars secret.....