This also was asked on Talk Bass, my answer:
It is MJLB4: Mark King Standard Long Scale Bass 4 string.
Explanation of the "model number"
First letter(s) = model name See: Alembic - Reference Pages
Second letters = scale length and instrument type.
Number = number of strings
Most Series I and II don't have the first letters, only I or II after the scale length. (fi: LSBII4 = Long Scale Bass Series II 4 string) Some with non standard Series I/II shapes do have the first two letters.
Edit: note they seem to add the S for scale on model numbers without the first two model name letters.
So my basses are:
SMB4 - Spoiler Medium Scale Bass 4 strings
OLB5 - Orion Long Scale Bass 5 strings. (I'm pretty sure some fretless basses also have an F in the model number, but it's not on my woodcard)
HLB5 - Elan Long Scale Bass 5 strings
ULBII5 - Europa Long Scale Bass Series II 5 strings
