Write to [email protected]. The mailbox is the single channel for corrections, source suggestions, missing model data and takedown requests.
A useful correction carries four things: the maker and model, the code as it is printed on the amplifier, the year you believe is right, and the document or page that supports it. Codes photographed on the amp are more useful than transcriptions, because letter cases and separators are often what the argument is about.
What can be verified here is whether a code matches the tables this reference holds and where those tables came from. What cannot be verified here is the physical state of an amplifier, its originality, or anything about a specific listing or sale.
If you hold a source this reference does not use — a factory bulletin, a service note, a catalogue page — send it and it will be considered on the same terms as the existing canon: it needs a date, an attribution and a specimen the rule actually fits.
Rights holders who believe material has been handled incorrectly can write to the same address with the specific page and the concern, and the affected passage will be reviewed.