Dwyer Model CSG Current/Voltage Signal Generator. It is a handheld tool used for troubleshooting and calibrating various devices.
It can generate a 0 to 10 V DC signal in 1-volt increments or a 0 to 20 mA signal in 1 mA increments.
It has a large, backlit LCD display for visibility in dimly lit areas.
The device can continuously ramp the output with user-selectable functions.
It is often sold with a carrying case, test leads with alligator clips, and a power supply.