Another pharmaceutical-related advertising FDC, this one from D. M Doyle Pharmaceutical Company of Minneapolis, Minn., for the #1251 Doctors Mayo issue of 1964. It is unusual in that the cachet is printed by offset lithography rather than by a method incorporating a steel-engraved impression and raised printing typically produced by ArtCraft. It makes me wonder if the company had the right to re-produce ArtCraft's design.
The product advertised, Meritene, is still sold today, but by Nestlé.
An FDC for the #1275 Adlai Stevenson issue of 1965 produced by the United Nations Association of the USA. As the UNA-USA group is a not-for-profit organization, I would imagine the envelope contained a request for a donation.