Really old Cases can fetch an impressive premium if the model is rare/collectable enough and old enough. If your friend bought it in 1970, it's possible it was made in 1970, but also possible that it was made in 1965-1969, and somewhat possible that it was made before that (1940-1964, but more likely in the later years). Before 1970 Case didn't date their knives with dots, but the general dates are discernible by the style of the tang stamp. Older is obviously more valuable, assuming same condition. I am by no means an expert, nor do I even know how early Case actually made canoes, but $400 seems rather optimistic to me. Like rma100 said, asking and selling prices are very different things. A person can ask whatever the heck they want, but that doesn't mean they're going to get it. You can look up any sort of collectable (like a mis-stamped Wisconsin quarter or a Vinyl Caped Jawa) on eBay and find all ranges of "Buy it now" prices, but that's not a good way to judge actual value. If the knife he saw at BLADE was "selling" at $400, but hadn't actually sold you can pretty much assume that he was expecting way too much.
Your best bet would be to figure out exactly (or as close as you can get) when the Canoe was made, and then watch eBay (or subscribe to worthpoint, which archives auctions) for similar knives and what they sell at.
