https://archive.org/stream/lettering00stev#page/38/mode/2up a mother lode of vintage alphabets. i could probably spend a month pulling ideas out of this book. https://archive.org/details/SpeedballTextBook the 16th edition of the speedball textbook is also available. in addition to many fonts, it has how-to-draw-a-turkey and great vintage layouts. if you want to surf around archive.org, you can find all kinds of great stuff. or you may go back to your envelopes.