Drawn thread embroidery, also known as pulled thread embroidery. Though this type of work was internationally practiced I believe this collection of samples is American. An entry in Wikipedia describes the technique as follows: “Drawn thread work is a form of counted-thread embroidery based on removing threads from the warp and/or the weft of a piece of even-weave fabric. The remaining threads are grouped or bundled together into a variety of patterns.”
Each of the nine samples measure approximately 5 by 5 inches to 5 1/2 by 5 1/2 inches, and are individually tacked to mat board. The full frame measurements are 24 inches square.