where to begin...
Within the realm of old canoes, there are many builders and many genres, and any one "collection" probably represents canoes and canoe-types and canoe-builders different from any other "collection"... depending on what makes bells go off for the individual collector.
If you're thinking of getting a canoe and want one that's "a good investment", the best advice is what they say on Antiques Roadshow: "buy what you like, not what you think someone else might buy."
As with anything anyone collects, once you've collected for a while, your tastes may refine and the collection may be honed to the ones you truly can't part with... for whatever reason that is. Down to that "important four (or forty)"!
This is a good discussion regarding value:
http://forums.wcha.org/showthread.php?t=57
It would be easier if you asked about a particular canoe or canoe company.
As for your question regarding canoe makers grading their canoes: many of the old canoe companies sold canoes in two or more grades. Old Town had AA grade (mahogany trimmed canoes) and CS grade ("common sense"). Morris had a single grade (mahogany trimmed, usually) after 1902 but sold a line of canoes with less expensive trim under a different name. Rushton's top-grade Indian Girl was trimmed in cherry. Is there a particular company you're interested in? Catalogs from many of the old companies are available on CDs available through
www.dragonflycanoe.com. They describe what was available.
My opinion: I doubt a "one off" would have the value of (for instance) a nicely restored [fill in the blanks: Old Town, EM White, Peterborough, Morris, Chestnut, Gerrish, Rice Lake, Rushton, etc on and on...] unless it was built or owned by someone famous or important, and that's why the canoe had value.
All of this is IMHO...
Kathy