@contrex,
Yes. I went out to buy some spinach for her indoors' sandwiches, and I concluded it must be the same as, or very similar to, our antique phrase "At the sign of".
At the sign of the crossed keys
at the sign of the cobbler
at the sign of the double eagle
at the sign of the Turk's head.
Probably dating back to the time when most people could not read.