TOD:
I love so many window , but I can agree that "1776" is one of the most memorable ever. Ditto "On the Twentieth Century" with its art deco design and the generous use of mylar!
I have both those window cards (originals)...along with "Mack and Mabel", "Dreamgirls," "Annie" (original and awards window cards), "Cabaret" (Tony window card), The Chelsea "Candide", "Dear World," "Woman of the Year," "A Little Night Music", "Company," "Sweeney Todd," and "Into the Woods" among many others. I also have reproductions of several window cards and posters I've found it nearly impossible to find originals of, including "The Music Man," "Follies" and "My Fair Lady."