I've got a Marshall straight bottom Basketweave cabinet that has four G12M 20W 75 hz speakers date coded to July 68, the speaker cabinet serial number is #134xx., Metal handles and imprint of small Marshall logo(missing) on grillcloth. Considering the 20W G12M speakers, does anyone know what particular model this cabinet is and it's application? It looks like there was some sort of emblem or cabinet model number or speaker power rating affixed in the upper left corner of the cabinet grillcloth but that's missing. Thanks!!