They have been replacement blades the Tamiya Modeler’s Knife Pro (product 74098).
• Narrow Chisel blades x5
• 0.55 mm dense.
• Narrower compared to the available these days chisel blade (Item 74101, Width: 4mm), and hence works extremely well in tighter areas.
• ideal for eliminating protrusion from flat parts of ribs and molds an such like.