From a photograph caption in the 2009 Organ Atlas: "The 1949 Holtkamp, the first 'Martini' model practice organ. The designers included Arthur Poister, Fenner Douglass, Grigg Fountain and Walter Holtkamp Sr. The details were worked out over cocktails one evening in the apartment of Douglass and Fountain, hence the model name."
Identified through information published in John Ferguson's Walter Holtkamp: American Organ Builder (DMA treatise, Eastman School of Music, 1976). Although neither Votteler-Holtkamp-Sparling nor their successor Holtkamp Organ Co. assigned Opus numbers to their instruments, this organ was identified in factory documents as Job number 1641. That number appears here as the Opus number of this instrument. Practice Organ