The 3-1734506-3: This is a 20-position dual-row female socket receptacle from the AMPMODU series, pitched at 0.079" (2.00mm) on both the row and column spacing.
Board-to-board stacking fit
In a vibration-prone assembly, a header with a locking ramp or board locks would add mechanical security, but for a stacked board pair inside a stationary enclosure the push-pull interface is sufficient. When selecting the mating header, verify the mated stack height against the enclosure clearance.
The base product number is 1734506.