A microchip system has two parts: a microchip and a scanner that reads it.
When the scanner is turned on, a radio wave signal is sent to the implanted chip. The chip sends it's number back to the scanner where you can easily read it in the viewing window.
The interaction between chip and scanner takes less than a second, allowing the identification of instruments and bows on demand. The Microchip Advantage
These chips are easily installed through the endpin hole into the end block of bowed instruments. A non-invasive process which hides the chip but can still easily be read. In bows it is implanted ahead of the screw shaft and can be read through all types of winding including silver and gold wire.
About the size of a grain of wild rice, this chip weighs only .06 gram.