One item I commonly find at garage and estate sales are the old recipe booklets that various companies, food industries and occasionally the local utility company would publish. They were either mailed or included with the product itself at the point of purchase. I don't know why people hung onto these, but I'm glad they did because I love them. I came across a cache of these at a sale this weekend. I'll go into depth with some of these at a later date.
"Good Cooking made Easy", Spry Vegetable Shortening, 1942