Paul, you are close. H station wire was 3 pair, but it used white/blue, white/orange and white/green pairs instead of tradional "quad" wire colors. It was also only available in 24 AWG.
D station wire was available in 22 or 24 AWG. I am pretty sure that J and L were only available in 22 AWG.
Yes, "JK" is the same thing as "D" station wire. I really don't know how this terminology came about. I do know that there was another type of quad wire from the late 1950's to the mid 1960's that was referred to as "JKT" that used a larger (20 AWG) conductor. Because of it's larger size, it really cannot be used with IDC connectors.
The only other lettered wire types that I can think of refer to cross connect wire. We have "F type that is 24 AWG and the twists are comparable to CAT3 rating, and it comes in a variety of colors and pair counts. "G" type is 22 AWG and is used in outdoor cross connect cabinets, but it's only made in white/violet single pair construction.
We also have "E" bridle wire, which is one pair or quad, but it's black vinyl insulated for each conductor. It is used to connect between outdoor terminals or terminals on poles. It was originally used to make the transition between open wire circuits and local drop wires.
