I have 2 rolls of vintage ribbon both of them are yellow (different shades), both of them are 1/2".  I am selling them wholesale, the full rolls.  I would estimate there would be between 4 - 8  yards on the smaller roll and between 8 - 12 yards on the larger one.  The ribbon looks like it may be taffeta - it could have a blend of fibers, I'm not sure.  There are a series of pin holes in the ribbons from where a 1/2" pin has secured it for years, this would not go through the full roll.  I tried to show the pin holes in my photo's.   I'm not sure if by wetting this you could get the fibers to hide the holes or not.  The holes get smaller as the roll is unwound.  The full rolls measure about 2" for the lighter yellow and , 2 1/2" for the darker shade.  The center wooden portion of that measurement on the spools is 1" & 1 1/4" on the spools.  There is some light staining on the outer layer of the ribbon.  

2 Vintage Ribbons on wood spools Shades of yellow 1/2"