I have recently received my Greatgrand father's Remington Model 17 as a Christmas gift!

I have been trying to research it and found they were made between 1921 and 1933. Can anyone help me determine the year of the gun from the serial number? The Serial Number is 9026. It also has "BO" above it does anyone have any idea what this stands for? I am really excited about this gift and any information anyone could offer would help me out!!
Thanks!