A paper in the recent edition of "Must-have Mustelines (incorporating Ferret Fanciers Monthly)" seems to be suggesting that experiments are taking place in the dark recesses of New Hampshire (a well-known haven for box players) on using specially bred Fishers as a substitute, after finding (by Experiment) that Beaver pelts were too watertight and didnt breathe sufficiently well. Also there is the marketing angle, after all, given the distinctive odour Who would buy a Beaver Concertina? The advantages in Fisher pelts being their Larger size and the superior quality. Maybe some enterprising Brit could start a trade with North America in the importing of animal pelts?