Is that bike all original, do you think?
Never heard of Dura Ace on a Grand Jubile. The stickers were included when you bought the parts, so it looks like someone upgraded and slapped a sticker on there. I wouldn't think the handlebar to be original.
I think the Grand Jubile went to Vitus tubing in 1977, so this would likely be 1976. It has Suntour GS dropouts. Hoo-friggin'-ray!
Nice original saddle.