The classic 100W Hylight-era Hiwatt head — the amp behind the "Hiwatt sound" of the 1970s.
Marks that can be entered for this maker: Serial number (plate), Transformer code.
Nothing predates 1960; 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 — hiwatt