All I can tell you is that it is post 1984, as I have a crank arm date coded 84 and it still has the fluting.
For the record, I think you got a decent deal, BB and all.
__________________
1971 Paramount P-13 Chrome
1973 Paramount P-15 Opaque Blue
1974 Raleigh Professional Blue Mink
1991 Waterford Paramount
Holland Titanium Dura Ace Group
Holland Titanium Ultegra Triple Group