Quantity   Component name
1 × Arduino Pro Mini
24 × PCB switches 6x6mm standard type
3 × 2 to 4.7K Resistors Precise value does not matter
8 × 1K Resistors Lower resistors draw too much current from Arduino
2 × 3461BS 7 Segment Displays
1 × PCB (or mess of wires) Kicad Schematic & Gerbers on project site