Colin Hinz offered to see what he could find out for is in regard to
replacements of the antique electrical switches and wanted to know the
dimensions. I don't have all the dimensions of all switches, but I can
tell you this much, Colin, almost all of them have a threaded collar
and fit inside of a box-- either wooden or cast iron.  Here are a few
dimensions, the largest is the old Duo-Art, which is the most used
switch for the duo-art. The smallest was taken off a Welte.

   Old Ampico (Stoddard) 1-1/4 "L. X 7/8" W. X 1" D. Uses threaded mtg.
collar 3/8" dia x 1/2" long. Pull-- on.

   Ampico, (a toggle with a drilled offset bat handle) 1-3/8" L. X 3/4"
W. X 1-1/4" D. Hard to find because most metal bat handles are hollow
and have a spring in them. This switch has mounting ears which are
1-7/8" on centers.

   Duo-Art ceramic shell switch  2" L. X 7/8" W. X 1-1/2" D. Has a
pull-on threaded wire which is attached to a 1/4" stem that pulls out
of the casing about 1/2" when on. (No threaded collar, but if we kept
the depth the same, the collar could possibly be used to mount the
switch, instead. Plenty of room.).

   Old (stencil) Welte and other motorized uprights  1-1/4" L. X 3/4"
W. X 1/2" D. wires attached. very small switch with large collar
measuring 1/2" dia threaded and 1/2" long. Pull travel is short-- about
1/8".

   Colin, I really believe that most of the bad switches are either of
the pull type with the bi-cone design and that stupid rolling spring
ring thingy that breaks, or those ceramic shell Duo-Art switches, in
which the rivet that holds the insulated metal washer wears out and
drops the washer off the end of the traveller. I have tried for hours
to fix both kinds without success. I would guess that if we could just
find a pull-on switch of reasonable dimensions, with a threaded collar
about 1/2" long that could be drilled and fitted with a threaded stem,
then we could retrofit it to just about anything that used the pull
type.

   The first size switch given here (old Ampico) shouldn't be too large
for just about any application, and if the switch is smaller, it won't
hurt anything, so I am thinking about two kinds of switches, generally.
One is a pull-on switch that can be drilled, the other is a bat handle
toggle that can be drilled.

Craig B.