Grand Guard Safe is a written note found in Dishonored 2.
Mr. Marletto from the Winslow Safe Company was able to re-open the regiment safe. We had to try different combinations for over two hours. Anyway, now we'll finally be able to distribute this week's pay.
Marletto advised us to set the combination to something the on-duty officers can remember. He suggested we use something like the average pay for a retired veteran, but I don't think triple zero makes a very secure combination. I just chose something else, and left it written in the Duke's office.
First Lieutenant Rosa Merquez
Grand Serkonan Guard
The note can be found during the mission The Grand Palace, in the office of the Guard Captain.