This is Tamiya's 1/35 scale Zimmerit Coating Applicator - Tamiya 35187.
During WWII, to overcome magnetic anti-tank mines, the German Army applied Zimmerit coating to their tanks. This set of photo-etched applicator blades allows you to easily apply Tamiya Polyester Putty to replicate the Zimmerit coating on your model in realistic terms. The set includes four types of applicator blades of varying sizes to allow you to apply a coating to both large and narrow surfaces.