'Codes' on Boarding Passes

[MR-B777]

Just wondering what some of the codes mean for different airlines that get written on boarding passes.

I have had "PCU" a couple of time on my BA boarding passes when travelling long haul.

[Dash-7 lover]

Possible club upgrade?? - This could also be commented at checkin for when the final PNL (passenger name list) gets taken on board. Check in agents can comment bookings as and when they see fit but with guidelines and without you knowing - it helps the dispatcher/cabin crew and boarding staff??? Could be totally wrong though!

SFU is suitable for upgrade.