are you sure it's not BP for black powder ??? it means barrel bushing, the pistol is a transition between colt 1911 commercial and series 70. your pistol was probably made in 1969.
Billy's Letters - 1911 was released on: USA: 4 December 1911
Love Whiskers and Letters - 1911 was released on: USA: 20 December 1911
On the frame
Donald M. Frame was born in 1911.
if your 1911 frame does not show a serial number then someone removed it and in so doing made the frame illegal. ATF regs require firearms to have serial number and if that serial # was removed the frame is the considered illegal to posses. however, the parts are NOT illegal and may be used to build another 1911 using another frame.
It should be marked on the frame.
The cast of The Stolen Letters - 1911 includes: Hay Plumb as Husband Gladys Sylvani as Wife
your 1911 was made by Colt in 1914. if your slide is marked 'springfield' it is the wrong slide for your Colt 1911. however, the wrong slide in use is not unusual.
No
Check the frame and barrel
It most likely means manufactured January, 1911.