We have perhaps the last Ampico B built.  It is from around 1942, three years or so after the factory was closed.  It's in a Steinway S and the stack in it is about the same as the one described by John Grant, with several lower notes and one upper note not included that normally were.  It was, from what I have read, due to space limitations of the piano.

Bob Taylor was involved with some stages of the work if you are interested in knowing more about the details than I am able to recall.

Larry Hollenberg