What you're looking at
This is a Furnas A-Line NEMA Size 0 contactor, order code A16N0-30-10-84. It's a 3-pole, non-reversing magnetic contactor rated 18 A, with a 120 VAC coil and a single normally-open auxiliary contact block built in. The 600 V rating covers motor and general-load switching in a NEMA-style panel.
The 18 A rating and NEMA Size 0 — what that means on the line
NEMA Size 0 is a standard frame size for contactors up to about 18 A full-load current for three-phase motors. For a typical 460 V motor, that's roughly a 7.5 HP motor load. The 120 VAC coil means it needs a control transformer or separate 120 V control circuit to pull in — common in legacy panel builds where the control voltage is separate from the motor power.
What you get in the box
The A16N0-30-10-84 includes one normally-open auxiliary contact block. That's a spare set of contacts for status feedback or interlocking. The contactor is 3-pole, non-reversing — meaning it switches all three phases together and only one direction. If you need reversing, you'd pair two of these with a mechanical interlock.