I liked Brian's definition of what is a variation. I think it all comes back to the printing process. If the "mistake" was intentionall corrected ... then it's a variation. If the mistake is just a one time printing error ... well ... I collect those ... but don't go crazy for them.
And Al, I respectfully disagree that there is a variant of every card. I've studied some sets very closely. There are cards that have reoccuring errors that have been corrected ... there are cards that have no reoccuring errors. The 1952 Mantle is the perfect example. That is a reoccuring difference. Jut like the House in my opinion.
But like you said Al ... everyone can make their own definitions and collect what they like. And with that said ... will you all stop collecting 1952 Topp Grey Backs - especially the Reiser!
Cheers,
Patrick