This is a genuine YHDC brand Non-Invasive AC Current Sensor Clamp, also know as a CT Clamp. BEWARE that many sellers who advertise this product actually ship clone and inferior quality clamps.
The SCT-013 is available in a couple of different versions. This version(SCT-013-000) is the most common one used, and will output 0 to 50mA when the measured wire is conducting 0 to 100A. It does NOT have an internal resistor. Normally it will be connected to a resistor on the target board that will convert the current (0-50mA) to a voltage.

Current transformers (CTs) are sensors that are used for measuring alternating current. They are particularly useful for measuring whole building electricity consumption (or generation for that matter). The split core is particularly suitable for DIY use it can be clipped straight on to either the live or neutral wire coming into the building without having to do any high voltage electrical work.

Common applications include current measurement, monitoring and protection of AC motor, lighting equipment, air compressor, etc.

Note: Colour might change due to different batches.

Use with OpenEnergyMonitor:
For information on how to use this sensor with OpenEnergyMonitor, [mx-link url="learn.openenergymonitor.org/electricity-monitoring/ct-sensors/yhdc-sct-013-000-ct-sensor-report"]

Use with IoTaWatt
This CT can be used with IoTaWatt. In IoTaWatt CT configuration, select SCT013. For details [mx-link url="docs.iotawatt.com/en/master/CTconfig.html#configuring-the-input-channels"]