My first guitar was a Michegan - an evil plywood flat-top with brass frets and a trapeze. I persuaded it to play easily by fabricating a bridge from a piece of firewood, but it never sounded like anything worth having. I got it from my cousin, who got it from a friend, who got it new from a newspaper ad around 1957 for about £4 7s 6d. I would guess that it was made in Holland by the people who used to make those Egmond monstrosities, and that B&SL were the people who ran the ads in the paper. Sounds like you've got the deluxe model if it's got real wood in the construction!