At a car boot sale a few weeks back I picked up a package of greetings cards - unused, still unfolded. They weren't cheap, but there are loads of them, in about 50 different designs. I particularly love the children's birthday cards - they're designed to be die-cut to shape so that once folded the front only part-covers the inside.
Aren't they sweet? I don't know exactly how old they are, but I think probably 1930s (some have definite Art Deco graphics).