Rolleiflex serial number

Havent been here for quite some time but hoping someone can enlighten me on a serial number.... AP/0553/162211 on a Rolleiflex TLR. I think it's a 'T' model. Has a Tessar 3.5 / 75 taking lens. This number is in the usual place.....above the main Rollei badge and just below the finder hood. There's another number below the taking lens.... T 2183797
which I think is more in line with that particular model but am confused by the the first one which doesn't appear to be a typical serial number .....

Any Rolleiflex experts out there ?

Bill

Picture? The Rolleiflex T has a distinctive bulge below the taking lens for the shutter release and synch socket.