Recently I acquired a set of older Fowler bench centers and a small
surface plate.

I have several questions concerning them...

While the bench centers itself appears to be well preserved after my
cleaning (it was quite dirty and I suspect it was used in a grinding
environment) I note that the mounted centers themselves seem to be
fixed in place. One end of the bench centers is spring loaded and this
mechanism works as expected. It was my understanding that the dead
centers themselves were removable. Considering that bench centers are
an accurate measuring tool, I thought I would ask for your advice
before I through ignorance ruined a good tool trying to remove what is
not meant to be removed. Are these centers meant to be removable and
if so, how would you remove them without damaging the overall unit?

The second item is a small surface plate measuring 18"x24"x3.25"
composed of black granite. This surface plate has a t-slot running
through the middle of the long axis of the plate with the dimensions
of 1" wide with a depth of 7/8". At the bottom of the slot located
3.25" from one end of the plate, there is a 3/4" hole which goes
through the plate. My questions are what is the t-slot used for, why
is the hole present and how is this plate used differently than a
normal surface plate?

I have spent considerable time checking the Net for answers to these
questions without success. Any information you can provide will help
both me and anyone else in the future.

I would also be interested in any suggestions or directions to
location on the Net that discuss how to properly care for these tools.
I wish to give them a much better home than from where they came from.

TIA

TMT