Vintage Motherload. This is why the web is going to change how we buy furnishings. We were tipped off to Past Present Future by a reader and can't believe was a huge resource it is.
Steven Mogol started Past Present Future in 1976, naming it after Al Stewart singing "The Road to Moscow," and has become the road to Mecca for those seeking American office furniture from 1862 to 1977. While he now has branched out into new and contemporary furniture, accessories, and art as well, PPF (what he calls it) stands out for its deep catalogue of vintage steel furniture.
With Sonrisa gone from NYC, this is your best bet. PPF has seating, desks, tables, files, credenzas, cabinets, bookcases, beds, lighting and artifacts like a disassembled 1890's mansion.
Prices run in the hundreds, not thousands for most of these items, and a fully restored Shaw-Walker Model 8310 with wood seat and slat back is $725 (pic above), while a mahogany stacking lawyers' bookcase (5-tier) goes for $1250. (Thanks, Randy!) MGR