I have 1 spare, bare PCB's for the SRSEII project, for the Märklin railbox/gleisbox.

The author describes the end product as follows:

"In my opinion, something is missing in the Märklin portfolio: A mini CS2 / CS3 without a screen that can control the model railway using existing tablets or smartphones. In my opinion, the CS2 / CS3 is too big and too expensive when it comes to controlling a small model railway. Many of you know the tinkering around BBB, BPi and RPi. Small disadvantage: an extra box."

See links below: http://lnxpps.de/can2udp/srseII/ https://github.com/GBert/misc/tree/master/srse2

Photo shows front and back side of the PCB.