The steel that was used for most of the brackets in a player piano is
known as "flat wire".  In the McMaster-Carr Catalog 106 they now have
this steel stock on page 3145, listed as cold-rolled round-edge flat
wire.  It is priced at about 15.00 per six foot section.

If you have ever need to make the hardware for a Seeburg or Coinola,
this is the steel that was used.  For example, in a Seeburg the steel
for the brackets that holds the mandolin rail are .066 inch thick by
3/8 wide.  This is McMaster-Carr part number 6511K22.

Don Teach
Shreveport Music Co., Inc.
1815 E. 70th Street
Shreveport, LA 71105