The 2007 Series 2 of the A21a - more power and a stiffer supply, still class A throughout.
Class-A unit: the chassis runs hot by design and needs free airflow. The supply capacitors are the usual failure point after 20+ years; Sugden still services the A21 line in the UK.
Marks that can be entered for this maker: Model / catalogue number, British capacitor code (Hunts, Mullard), Japanese capacitor code (Nichicon, Chemi-Con, ELNA), EIA component code, Version & era marker.
Nothing predates 2007; 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: Sugden — official ampography · HiFi Shark — live listings aggregator