The sign on the left wall appears to say
(as best I can make out)
"Our pieces are signed (BB) BECKY BROWN
and for KARL MARTZ (KM)
and simply
MARTZ POTTERY
for pieces we both have worked on."
It was undoubtedly painted by Karl
using tempra poster paints.
He was a skilled sign painter.
The large plate on the right wall is still in the family collection. Whereabouts of other pieces in this photo are unknown.
Photographer unknown
(deckle edged print).