Versions
MIL-PRF-5606J - The most recent version of the spec, established in 2018.
MIL-PRF-5606H - Previous version of the spec. First established in 2002 with 3 further amendments in 2003, 2005 and 2006.
MIL-H-5606A - Established in 1957, an early version of the spec. With MIL = Military, H = Hydraulic Oil, 5606 = Unique Identification Number, A = Version.