The problem is that documentation gets dumped or lost, and people don't realise someone involved needs to make some kind of record of what happened, etc... until it is far too late. I was lucky to some extent in that I realised whilst a few of the older people involved were still around that the history would 'evaporate' unless *someone* made an effort to record and publish it. But by then all the old works documents had gone and much had been forgotten.
What annoys me is that academic historians seem to take zero interest in areas like UK manufacturing history of such items. Some museums collect kit. But no-one collects the memories, paperwork, etc, from the people involved. The result is that we end up with a few old adverts, pamphlets, etc, that don't reveal the details of how things were actually designed or made, or who did what.
WW2 is a particular problem because the changes aren't shown clearly by normal adverts or magazine articles of the time. So once the people working there at the time have gone, who knows *what* they did as 'war work'?
