1925 was a rather sparse year for commemorative stamps. Only five were issued that year, a set of three Lexington-Concord stamps commemorating the early years of the Revolutionary War and a two stamp Norse American set. The Lexington-Concord set was a nice looking set, but nothing special design wise. The second set, although commemorating a somewhat more esoteric event, had very striking designs. Both stamps were printed in both black and colored ink and featured sailing ships, one a 19th century Norwegian sloop (the Restaurationen) and the other a Viking ship.
Unfortunately, these stamps had smaller print runs than many of the other stamps of the period and tend to be a bit more expensive, although not dreadfully so. It looks like a mint two cent red design runs about five dollars and the blue five cent design around fifteen to twenty dollars. Used stamps are cheaper of course, and there are probably significant variations in price due to centering, etc. (the above prices were gathered from a quick scan of eBay!).