Wikipedia
Union label
A union label (sometimes called a union bug) is a label, mark or emblem which advertises that the employees who make a product or provide a service are represented by the labor union or group of unions whose label appears, in order to attract customers who prefer to buy union-made products. The term "union bug" is frequently used to describe a minuscule union label appearing on printed materials, which supposedly resembles a small insect.
Usage examples of "union label".
Gore also told a union gathering that his mother used to sing lullabies to him as an infant including Look for the Union Label.
No more were they worried by slack times, strike and lock out, and the union label.