Researching in company archives and other primary sources - how to get started?

[Schneiderman]

........... I would say success is more hit and miss with the smaller sites.

Ah yes, but that is where the nuggets of purest aviation gold (or green!) can often be found, at least for pre-war projects. For these smaller museums and archives you are dealing mostly with volunteers, like me, rather than professionals, so a degree of patience and friendliness pays dividends. Keeping a watchful eye on ebay and other online sites can, indeed does, also yield the occasional gem, albeit that the prices can sometimes make you wince. I'm still sitting on a small treasure trove of bits and pieces just waiting for a few extras before making their way into articles.