SP = "SPECIAL"
MANY Wurlitzer instruments were SPECIALs.
Some were a variant of a standard style is which case they would be called something like a "D SP".
Others were true SPECIALs with no clear relationship to a standard model. These were called "SP".
In most cases the full specification for these SPs is not available.
If you do have this information please send it in so that it can be recorded with the other
information for that instrument.