Scientific trade literature is a unique and uniquely valuable category of historical evidence. But it has not always been so highly regarded. Being commercial documents, catalogs have traditionally had a hard time fitting into library or archive collections. Even the companies that printed these catalogs expected their usefulness to end as soon as the next edition was printed. That's why so many of them were printed on the cheapest paper available. In many ways it's not surprising that so few of them have survived - or that when they have survived, their existence has gone unnoticed.