Back before lettering was more commonly referred to as fonts a couple of sources made a big impact on the styles (s) of hand lettering that I do. One was the amazing and unequaled 1950s - 1960s output of the Photo-Lettering company out of New York. The other was the ads in the back of black and white magazines published by Warren Publishing.
For samples from both giants why not head on over to my most recent post at the image sharing site Flickr. You'll be glad you did.