1x12 flip-top Portaflex combo.
Ampeg's own dating/support text carries an explicit warning: lethal voltage is stored inside tube amplifiers even after power-off — the SVT and V-series in particular should not have their chassis opened by anyone without experience. Read the serial from the outside.
Marks that can be entered for this maker: Serial number (plate), Transformer code.
Nothing predates 1961; components only push the date later.
Sold-price aggregates are not collected yet, so the archive gives no figure — condition, originality of the transformers and a documented recap move this model more than any list price.
Evidence: Blue Book of Guitar Values — ampeg