90 mm Apo-Rodagon

I'm looking at buying a used 90 mm.   Serial #10319867

Can Bob Salomon tell me when this was manufactured?

Is there two different apo-rodagon lenses, an "N" version and an non-"N"
version?

In the group's opinion, could I use the 90mm f4 for 6X4.5 enlarging to 20X24?
(using a Saunders XLG enlarger).  



Thanks,

John