one thing I have trouble with.
takahashi does FC's, FS's, DL's, TSA's, etc. ouffff, for someone who starts it is cryingonfusing.
TSA120 is a 120mm aperture triplet, only that model made now.
FCs are all doublets of 60, 75 & 100mm apertures, and varying focal lengths.
DC, DF are suffixes to the FC-100mm models of 750mm length.
DL is for the 900mm length model.
DZ is for the 800mm model, replacing the 3 described above.
FS are old doublet models of various sizes no longer made. TSA-102mm triplets are no longer made.