Kodak 3 x 3" (75 x 75mm) #47 Deep Blue Wratten Gel Filter for Tricolor/Color Separation Work - A deep blue filter that accentuates haze and fog. Also used in dye transfer printing, and for contrast effects (lightens blue tones).
Most Kodak gelatin filters are available in 3 x 3" (75 x 75mm), 4 x 4" (100 x 100mm), 6 x 6" (150 x 150mm), and 14 x 18" (350 x 450mm).
Filter factor 8 (+3 stops).