OED goes into quite a lot of detail.
"riband, n.". OED Online. June 2012. Oxford University Press. 20 August
2012 <
http://www.oed.com/viewdictionaryentry/Entry/165460>.
'Riband' seems to have the same ultimate origin as 'ribbon', but the
definitions for the variant with "an excrescent final dental consonant"
indicate special meanings that are still current in my experience,
despite the note that this variant is "Now chiefly arch. or regional."
It is notable that OED gives 'Riband' an entry of its own, rather than
bury it under the more frequently used 'ribbon'.
Definition 1c is the usage of 'riband' I'm most familiar with:-
c. = ribbon n. 2a. Also in later use: a prize awarded to the winner of
a competition; a symbol of distinction, performance, quality, etc.; =
ribbon n. 2b. Esp. in blue riband (see blue ribbon n.).
See also red riband at red ribbon n. 1a.
Nestlé make a "Blue Riband" wafer biscuit, and Wikipedia's
disambiguation page offers several examples of the 'reward' usage
<
https://en.wikipedia.org/wiki/Blue_Riband_(disambiguation)>.
I would hesitate to use 'riband' in any other context, or as a
technical term in heraldry (OED's definition 2) or to describe a
striped arrow (as loosed from a bow; OED's definition 3b). 'Ribbon' is
better in all other situations - although 'riband' is not 'wrong'.
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-- Whiskers
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