1930 Carnival Fair Art Pottery Chalkware Union Stamp

Carnival Fair Art Pottery Chalkware Union Workers Stamp on Bottom .    I Believe this is an old Carnival / Fair Piece which was handed out as prizes .   Not certain of age, 1930's maybe before .  Stamp on bottom is partially gone, therefore could not find any valid information .  It Reads ?? / Looks Like - Union Label - Plant Workers and a Nude Lady in Center of Stamp .  Any information on the Union stamp is very welcome .

Condition:    Very Good for Age .   I do not see any gross damage , No chips , cracks or repairs .  A couple of small fleabites / paint flaked off .