From the speaker date code and other clues, this is a mid 1957/mid 1958 Ampeg M-12 Mercury. Likely a product of Ampeg’s transitional period during their move to Woodside, NY. Definitely a special amp with lots of character. Groovy “Pollocked” grill cloth. Jensen Alnico 5 speaker. And no tolex here. The original cream bookbinding cloth with watermelon-red painted grill frame detail, still visible, can be found beneath a vintage paint job. The potentiometers on this amp date to back to 1950 while other components used, such as the parallel flexohm resistors went out of production by 1940. Assumed to be a “prototype” due to the odd “non-production” parts, unrefined layout and primitive circuit design with notably sparse tone stack. In addition to the unique cloth covering, the cabinet appears to have been built of recycled materials and features an unusual solid back panel. The Woodside NY label is present but lacks a serial number.