The Hirose DF12E(3.0)-20DP-0.5V(81) is a 20-position, 2-row board-to-board mezzanine header with a 0.50 mm pitch.
The 20 positions in two rows give a compact footprint roughly 5 mm by 2.30 mm above the board.
Replacement and Cross-Reference
The DF12 series includes many 20-position, 0.50 mm pitch headers with varying stacking heights and plating options — but without a documented cross-reference from Hirose, any substitution must be verified against the original board layout and mating receptacle. The closest parametric match within the DF12 family would share the 20 positions, 0.50 mm pitch, 2 rows, and 3 mm stacking height, but the exact part number depends on the specific variant suffix.