You can check this my carefully lifting the display and looking on the back of it. Look for a barcode starting with "TEM" or "VEM".
If the seventh character of the barcode is 'B', then you have a COG 2. Follow these instructions for building the driver:
make rpi-clean make COG_VERSION=V2 rpi sudo make COG_VERSION=V2 rpi-install sudo reboot
% cat /dev/epd/panel EPD 2.7 264x176 COG 2 % echo C > /dev/epd/command
make bb-clean make COG_VERSION=V2 bb make COG_VERSION=V2 bb-install reboot
See https://forums.adafruit.com/viewtopic.php?f=22&t=105673 for a possible fix!