Dave K
I live for the CABE
I've had 40s with spears and later style tank graphic and currently have a 40 with the earlier style graphic and scrolls. I think my 40 with spears was a dlx w-springer and a Chicago cycle bike. My scroll 40 is a Henderson so in short, I don't think the dart or scroll should be used as an accurate indicator of age.
Yes I agree 40s (and 41s) can go both ways on the frame paint and tank paint but have not personally seen any 39 DX bikes with the graphic and scrolls so best guess is 40 on Zacks bike. Could also be an odd ball 41 built out with 40 parts but at that point it is more or less a 40 anyway.