My Grandfather Neill's WW2 Selective Service Classification Record indicates he was classified as a IIB, a IIIA, and a IVA. Selective Service sent me a list of classifications, but I also found them online.
The IIB meant deferred in war production.
The IIIA meant deferred for dependency reasons (my grandmother and their two children).
The IVA meant deferred by reason of age.
Nothing shocking, but interesting nonetheless.