Two different sized standard steering wheel horn rims?

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There's this guy selling a standard-type steering wheel horn rim on Ebay that I'd like to buy and he put the diameter of the horn rim down as 11 1/2" when the auction was first started. Since I've screwed myself over once or twice by making assumptions I decide it's best to double check the diameter of my horn rim, right? So I go out to the garage and discover that mine measures 11 3/4" OD. Huh? So I email the guy and say his looks like the one for my 68 Charger only mine measures 11 3/4" and he replies saying oh yea, it is 11 3/4" and sorry for the mixup (then he immediately jacks the price by $20 which pisses me off but then he feels bad so he lowers it back down). Anyway, I'm thinking I'm on my way to getting a good horn rim, right? Wrong.

All is well until some 67 GTX guy chimes in and says hey, my horn rim measures 11 1/2" and I want to make sure yours is not 1/4" too big. So the seller apparently measures the rim once again and this time gets 11 1/2" like he supposedly did the first time. After GTX guy hears that news he makes the opening bid and now I'm left wondering how the horn rim is both 11 1/2" and 11 3/4" depending on which buyer the seller is talking to.

Anyway, here's the question. Did Chrysler really make two horn rims that were 1/4" different in diameter or is there a problem with someone's ability to read a tape measure? When I say standard wheel I mean the one pictured below...

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Thanks for the help. The auction just ended and I won so I hope it's right.