That writing on the lock was from me 5g for 5 gauge and 110 for the lock, I adapted a 110 and 6 gauge curtain to suit the fortress keys, but never having seen one couldn't figure out how it would work from both sides unless you used a and b section keys, didn't realise that the curtain is profiled to allow entry from both blank profiles unless it is the 3g135 case itself that stops the wrong key profile from entering.
Thanks for putting that picture up Tom.