Thanks for the info, Stan! I expected it would date to either late 60's or sometime before mid 70's, but I wasn't sure.
Dan, I hadn't heard of the nib name but "Supra" certainly fits.

This nib style is seen on most of the Pilot Custom pens. I know they came in the standard <F>, <M>, <B> sizes (I have all 3), but I wonder if they ever had oblique nibs. The great thing is that Pilot was consistent with the nib section size and clutch ring diameter--I can easily interchange the nib with any Custom Pilot (so if the nib ever got seriously damaged, I could easily get a replacement by cannibalizing another Custom pen).
Also, the Supra nib came in either white or yellow gold. I have a white broad nib on a Pilot Elite that I've interchanged with this Bamboo model--matches the barrel nicely.
Thanks for the compliments everyone -- glad I could give you a glimpse back into Pilot history.