The Amphenol 86503-150HLF is a 50-position, dual-row unshrouded header from the BergStik® II series, built on the standard 0.100" (2.54 mm) pitch. It's a through-hole, solder-terminated board-to-board interconnect with male square pins.
The dual-row layout with 0.100" row spacing means the footprint is a 2 x 25 grid, so the board area is about 2.5" long by 0.2" wide, not counting the solder tails.
The 0.250" mating length gives good wipe before the contact beams bottom out. No board locks or alignment pegs — the solder joints take the shear load, so the board needs adequate pad adhesion for vibration environments.