The 20021311-00040T4LF: This is a 40-position, dual-row female socket receptacle from the Minitek127® 1.27mm series, designed for board-to-board stacking. The mating finish is gold at 10.0 µinch (0.25 µm) over phosphor bronze contacts. That's a serviceable plating grade for moderate mating cycles — think a few dozen field disconnects over the product life, not a daily-cycled test fixture.
The part is RoHS compliant.
40 vs 44 Positions — When the BOM Needs a Sibling
It shares the same 1.27 mm pitch, dual-row layout, gold mating finish, through-hole termination, and UL94 V-0 housing. If your board layout has the extra four holes, it's a drop-in swap for the same footprint. Other active siblings include 36-position (20021311-00036T4LF) and 34-position (20021311-00034T4LF) versions, identical in all other respects.