I recently picked up a large estate lot at auction from an auction house that is large but not one of the usual suspects selling boxes of "stuff". One of the items in a carton was a plastic tub full of old envelopes from all of the legendary dealers like Klein, Stern, Mozian, Harmer and many others. Each envelope has a country name on it. Within the envelopes are old and crumbling manila stockcards packed with stamps. Nothing past the 1930's and most of the concentration on the 19th century with duplication of even the highest values. Mostly used with a large variety of SON cds. A mind blowing asemblage to view and explore. I just began in the past couple of days and have made little headway. If this type of find is your thing but you are having difficulty finding it keep searching. There are still great things which are coming to light which have been squirreled away.
A few quick photos as an example (more to come):


