It hears that Schwalbach had done the four-bank keyboard and handed it to Sholes around the spring of 1871.

http://groups.yahoo.com/group/TYPEWRITERS/message/49446
I have a quick question about some terminology I've heard. I've heard some
machines referred to as 1, 2, 3, or 4 bank machines--what exactly does this
mean?

The saying of Schwalbach hears as follows:

http://content.wisconsinhistory.org/cdm4/document.php?CISOROOT=%2Fwmh&CISOPTR=17986&REC=0&CISOBOX=four-bank
p.398

his criticisms annoyed sholes but impelled him to go on making improvements the inventor soon adopted a new keyboard of Schwalbach's devising which consisted of four rows of metal key levers and buttons set in ascending banks.[18]

[18] Schwalbach afterwards said that " while he continued to work for Mr. Sholes for $3.00 a day during the winter of 1870 he took up the work independently in his home he worked out the four-bank key board and in the spring of 1871 he laid his completed model before messrs sholes and glidden howard in typewriter topics 3:8