I believe all of these old Red Cross pins date to the World War I era; some are marked 1919, one 1920, and I think the rest are about the same age, maybe a few a bit older. Most of the backs are stamped, including with the following: "American Art Works, Coshocton, Ohio"; "Gerighty & Company, Chicago, IL"; "Greenduck Metal Stamping Co"; "The Whitehead & Hoag Co. Newark, NJ"; and JL Lynch, Chicago, IL. Hard to beat this iconic logo, I think, and great for channeling the spirit of Clara Barton!
These vary in size a bit, but average about 5/8" across. Sold as mixes sets of 5, though just note on your order if you have specific preferences.