I found the information I was seeking. It turns out the it wasn't on the BB, but on a couple of other sites I had been reading.
It seems that the Jaeger speedometers can be adjusted, but it isn't as easy a process as I seemed to recall. I originally came across the instructions long before I decided that my speedo really needed some attention.
As Hoygs suggested it is going to be a fussy, trial and error type of operation, so I'll probably just live with the readings as they are until I'm getting ready to put the car away again for winter storage. I don't need a dial to tell me how fast I'm going.
--Toronto