Description of the IBM 650
"The IBM Magnetic Drum Calculator is a numeric decimal machine and was designed with the principle with ease of use as a basic consideration. Thus checking is provided throughout the machine, a modern set of stored programs is used, large capacity is provided, and a carefully designed operator's control console provides direct communication between the operator and the calculator. Imaginative engineering has led to compact design, high reliability, and moderate cost.
The Magnetic Drum Calculator is available in two models. Model 1 has
the capacity for 10,000 decimal digits of storage (1,000 words) and Model 2 has
the capacity for 20,000 decimal digits of storage (2,000 words). A word
can be regarded either as representing ten decimal digits and sign or as a two
address instruction." [Annals of the History of Computing, Vol. 8 #