In the 110611 MMD Bill Maguire said:

    "Hammers used to be advertised and sold as 12 lb. or 14 lb., etc.
    I'm no engineer, but it seems this was a very inaccurate method for
    estimating what the weight of a hammer will be after its glued, and
    with the various woods they used for moldings."

The 12 lb., 14 lb., etc. weight of hammers refers to the weight of the
sheet of felt from which the set of hammers is made.  A 14 lb. sheet
will be thicker than a 12 lb. sheet, obviously.  Also, the entire sheet
of felt is not used in making one set of hammers.  This is still a
legitimate way of referring to hammer sets, because a heavier weight
will also make a heavier hammer.

Mark Ritzenhein