Updated...... please re-read this post
The serial port is just for programming the chip that will already be done
http://team-xecuter.com/x2prog/ the flash kit programming via the serial port hooked up to a PC with a serial LTP port (that was used for old printers)
You will not have any idea what he/she has flashed into each bank so just use what it is set up to or you can try each 256 setup and see if there are any differences
More info at
http://z6.invisionfree.com/Supreme_Mods/ar/t10.htm it's just an install instruction but it looks like your setup so yeah it could very well be the 2.3b pro version, the 2.1 pro is not really any different (this also has info on the switches)
At the moment yours is not setup correctly, the switches are wrong, I thought it was set to bank 3 but the switches are the total opposite to the Bank 3 setup
P.S. the mod chip is disabled at the moment to enable it lift the broken switch up to the on pos
Made a better image to use for your switches