This timeline of binary prefixes lists events in the history of the evolution, development, and use of units of measure that are germane to the definition of the binary prefixes by the International Electrotechnical Commission (IEC) in 1998,[1][2] used primarily with units of information such as the bit and the byte.
Binary memory had sizes of powers of two or small multiples thereof.
In this context, 'K' or 'k' was sometimes used to denote multiples of 1024 units or just the approximate size, e.g., either '64K' or '65K' for 65536 (216).
The same data sheet uses MByte in a decimal sense.
Shugart Associates, one of the leading FD companies used k in a decimal sense.