ATM Pyrex glass questions

["Bertapelle, Ken" <Bertapelle.Ken@tci.com>]

Can anyone out there answer these questions?  TIA.

What kind of pyrex should one ask for when purchasing a pyrex telescope
blank?
Mel's page suggests "fine annealed pyrex, #7740".  The Corning web site
doesn't
have this designation.  Corning offers "barium borosilicate, # 7059".  Does
anyone 
know what these numbers mean, especially their relevance to mirror
properties?

What is the difference between coarse annealed and fine annealed pyrex?  Is
it
the number of bubbles in the material?  Are "coarse annealed" and "fine
annealed" well known terms, or should numeric descriptors, like the above,
be
used to specify the material?

Are the thermal expansion properties of all pyrex materials (coarse and
fine) the
same?

- KenB