This item is a Sutron Shaft Encoder (Model 56-0540) used for measuring water levels in rivers, streams, and reservoirs.
It features a 2-line, 8-character built-in display.
It communicates using SDI-12, RS-232, or SDI-12 over RS485 protocols.
The encoder has a resolution of 400 counts per revolution.
It is designed for low power consumption, operating on 12VDC.