This one is for the lens experts.

Ok, we know that there is the order of the lenses, from 1st to 6th. Then there are the various styles of lenses. Some styles come in more than one order, i.e. a photo posted recently by Gary Martin of Bodie Island's first order lens looks very much like the HL 4th order lens. Perhaps only the higer order lenses came in diferent styles? So...my question is how many different combinations of lenses are/were there?