Need some royalty-free vocal samples

I’m looking for some vocal sound samples of a rather specific type - snippets from old-style radio and TV ads - sort of 1950s (not 20s)-style (usually male) voice extolling the virtues of some product or other.

Does anyone know where I can download some of these for free? - they must be public domain.

If you feel like taking the sound from movie files, the Prelinger Archive is a great place to start.

Thanks for that; they also have a section on advertising that looks like it will fit the bill exactly.