Just to clarify....
Typically, NFA weapons with the designation "pre-86" are weapons imported into the US after the 1968 GCA took effect. These cannot be transferred to individuals - only Special Occupational Tax holders, police agencies, and government agencies.
I'm sure that Son of HK meant a licensed, fully transferable MP-5 manufactured before 1986 when the FOPA was passed restricting civilian ownership to current MG inventories only.
The reason I mention this : designated Pre-86 NFA weapons are usually much cheaper to buy than fully transferable models - commercially, the fully transferable models have more value than a model that can only be owned by SOTs, police, and govt.
Fully transferable MP-5s, depending on configuration, currently run $7k+; Pre-86 samples $4k+; Post-86 samples $1.5k+ (post '86 samples cannot be kept by SOT holders once their SOT status expires).