KEEP TABLE CLEAN, Red on White Stencil Painted Steel Sign

Something related to where this sign lived on December 12, 1974 cost $6.53 per __ (?), which someone wrote in pencil right on it. I'd like to think it lived in the studio of Donald Judd, say, who was both ordering lots of industrial material and needing the work table to be clean! Whatever the case, a satisfyingly minimalist, matter of fact sign, in perfect red on creamy white comb. On steel plate, with two holes at bottom for mounting.

7" w x 6" t, good condition, all the better for for the wear and aging to the paint and pencil writing all over it.