The two are "cut squares" from postal cards. They will be found in the "UX" postal card section of the Postal Stationery back of the book section of the Scott US Specialized Catalog. You will also find the designs in the "UY" postal reply card section as well.
Postal Stationery by memory lists in this order: Regular envelopes (including wrappers), airmail envelopes, official envelopes, regular postal cards, airmail postal cards, regular reply postal cards, airmail reply postal cards, official postal cards.
I do not have my Scott Worldwide Volume 1 handy to verify that postal cards are listed there. The US listings in the volume 1 are streamlined down from the Specialized. Same goes for the US in the Scott Classic.
Edit to add:
Quote:
Is there another place I can look?
Higgins & Gage World Postal Stationery Catalog
United States Postal Card Catalog
See others here--
https://www.upss.org/code/publications.phphttps://goscf.com/t/80868