Yup, one of these is well aged. Made a less then favorable trade. And slightly over paid on the other, eBay. lol
Bottom one has a spot that looks as if it was placed against a heater. Been meaning to get better pix of these.
Oh, both are 3x6
Did not look at link Brent posted, but this is what I found for clear.
http://www.eplastics.com/Plastic/Plexiglass_Acrylic?gclid=CLCa8IeUu6wCFYHe4Aod9Sfepw