I used to work for Gilkey so I know the window well. They are a good decent window, but I'd take Schuco any day. Schuco blows it away on features, appearance, fit & finish, and spacer technology.
I've also heard Gilkey radio ads broadcast all over Chicagoland stating they are number one out of 22,000 tested with the NFRC.
The only rating they could be possibly thinking of bragging on is a U-value rating. The 22,000 windows tested means they are also considering every type of window of every manufacturer,... i.e. doublehung, casement, picture window.
The Gilkey has an impressive .16 U-value rating on one of it's picture windows, so that must be the window they are using to make their claim.
Only one problem......Schuco has a picture window with a .14 U-value.
I hope no state attorney general finds out......they could get into trouble for false advertising!