The base sixteen number system was used with the design of the Monrobot XI computer in 1959 by the Monroe Calculator Co. in Orange, New Jersey.
The system was called Sexadecimal, using the numbers 0-9 and then S, T, U, V, W, X to complete set. The IBM Model B typewriter was used and the keyboard entry interpreted S-X. The IBM 1620 Model I used the IBM Model B typewriter but I do not know about number entry, even though I began learning about and working with the 1620 in 1962.
The Monrobot XI used 8 channel paper tape input and output. An assembler was initially written and it provided for a source tape to be created, then the source tape was processed twice to produce an object tape that contained the machine language that could then be loaded and executed when running the program.
I first learned about the Monrobot XI in 1962 and then began working with it in 1965 until it came to an end in 1974. The entire product line was purchased by Computer Property Corp. in Hanover, NJ in 1967. I worked with the software side known as Systems Design, Inc. In 1967 I re-wrote and improved another assembler that started at Monroe.
I also wrote a dis-assembler that would accept as input an object tape and create an assembler source tape. References for absolute disk memory locations and other functions were created so that the new source tape could be edited and re-processed to produce a new object tape. During the years many installations would send us object tapes and request modifications to the programs, so it was well worth the effort initially put forth to write such a program.
The Monrobot XI had a magnetic disk with 2,048 32 bit words, using fixed heads. There was also a magnetic card that was the same size as the 80 column Hollerith card that contained 96 32 bit words that were addressable.
Photos of the Monrobot XI are on "flickr.com" using the search term "monrobot"
Donald O. Caselli