Triangular aerial recognition roundel on subchaser SC 208, and on SC 323

Roundel on subchaser SC 208:

Photograph of SC 208, courtesy of Bobbie Miller, daughter-in-law of SC 208 crewman Henry Miller.

Roundel on SC 323. Photo caption: "The USS 323 in rough weather off Holyhead."

Photograph of SC 323. T. Woofenden Collection.

Known examples of this roundel style:
SC 208 (served at Plymouth and Queenstown, shown above in unidentified location.)
SC 323 (served at Plymouth and Queenstown, shown above near Holyhead, Wales)