You can guarantee you will keep your coupon, by buying a converter box online. Example:
http://search.solidsignal.com/?site=...+Converter+Box
You can enter the coupon code directly at checkout. I ordered one of the Philco units just to compare and contrast makes (and to put on my Philco 50T when it's ready). Would like a Zenith too (for the Zenith Roundie), but haven't found one locally yet.