This is a rare, and very handy, export model, the early version with the internal tag board to switch voltages.  I'm going to assume you know all about the 6G6-B Bassman, the one favoured by Brian Setzer & Little Barrie and a whole host of other great guitarists.  This a great one, the head is almost completely original.  The back panel is a modern replacement.  Transformers, choke, etc, all original.  Most of the original paper caps have been replaced, as you would expect.  Someone's done quite a nice job of re-stuffing the cathode bypass caps with modern replacements.  This is about the best possible head you could find for a UK user.  Also available with a cab at a discount.