(-)Flat head machine screw(Coarse Stainless steel Unplated 2 X 6

The head of a round machine screw is nearly hemispherical in shape, similar to today's truss head machine screw. The flat head machine screw has a low-profile cylindrical head. It was commonly manufactured in the past due to its simple production method.
Machine Screw Head Dimensions List　Encyclopedia of Round & Flat Head Machine Screws

• Slotted (-) flat head machine screw, Coarse pitch
• Nominal diameter (d): M2
• Length under head (ℓ): 6.0
• Pitch (P): 0.4
• Head diameter (dk): Nominal 3.5, Tolerance 0,-0.4
• Head height (k): Nominal 1.3, Tolerance ±0.1
• Slot width (n): Reference 0.6
• Slot depth (t): Reference 0.7