This is a Jackscrew, which is used to secure an SMA/SMC connector to a circuit board. It is made by TE Connectivity, a global leader in connectivity and sensor solutions, and part of its SMA/SMC family of products. The 5-1393104-9 part number is a Brass and 304 Stainless Steel Jackscrew, which is 0.376" long and has a head diameter of 0.243". It is designed to fit SMA connectors with a body size of 6.0mm, 6.4mm, and 7.0mm. The jackscrew has a M2.5 thread with a 0.45mm pitch and is not soldered to the board.