Lord & Burnham designed Phipps Conservatory in 1892, which was probably their biggest commission ever; and in this 1896 advertisement for their services, we see them showing a model conservatory that is very much like one of the wings of Phipps.
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Lord & Burnham, Horticultural Architects and Builders
From the American Architect and Building News, July 25, 1896. 
Southeast wing of Phipps Conservatory, with John Massey Rhind’s Robert Burns. -
Hotel Schenley Advertisement from 1929
Pittsburgh Post-Gazette, January 29, 1929, page 10. Note the exaggerated height; compare it to the proportions in old Pa Pitt’s pictures.