What this 4-position IDC receptacle is
It sits at the cable end of a wire-to-board interconnect, mating with a 0.100" pitch SL header.
IDC termination and wire fit
It accepts 24 AWG wire, either as discrete strands or as a ribbon cable. The free-hanging (in-line) housing lets it float at the cable end rather than locking to a panel or board.
The female sockets carry a 150.0 µ" (3.81 µm) tin finish on the contact surface. That is a heavy plating — well above the typical 30–50 µ" tin flash found on low-cycle connectors. For an IDC termination, the thick tin serves two purposes: it survives the wiping action during cable insertion without galling, and it maintains a gas-tight interface at the displacement slot over temperature cycling.