Ansco Turner Reich question

My 8x10 Ansco has arrived complete with 8x10 Tuner Reich servies iv anastigmat whats the difference between the series ii T/R's (which are convertible) and the series iv's my lens is on a betax 4 it is marked 8x10 so im guessing its about 300mm f/l it's f 6.3 the shutter has only one f scale (not 3 as per the convertible's ) any one have any information on these lenses?
( no sign of the dreaded canada balsam seperation its a late(?) 20******* serial No built in Fairport NY)

In case you haven't seen it here is an older catalog: http://www.cameraeccentric.com/html/info/korona_2.html Not sure it will answer your questions.

Thanks that helps a little - from that catalogue im guessing that these lens are fixed and not convertible like the series ii T/R's ive cleaned and reground the G/G the and pointed the camera down the garden the lens certainly covers the full 8x10 it appears reasonably sharp