This is about two microcontroller boards I received some time ago from Vesta Technology: the Mercury 16 which uses a Microchip PIC16F1947 processor, and the Mercury 18, which uses a Microchip PIC18F66K90 processor. These processors are sufficiently compatible that they both use the same circuit board.

From the hardware manual:

Mercury is a family of small PIC-based Single-Board Computers (SBCs) intended for embedded monitoring and control applications. They are designed to be compatible with Arduino shields while providing enhanced I/O capabilities.