From the OHS PC Database, derived from A Guide to North American Organbuilders by David H. Fox (Organ Historical Society, 1991) -

Succeeded Votteler-Holtkamp-Sparling Organ Co. of Cleveland, Ohio, 1951; active in 1989.

Staff: Charles B. Fisk; Frank L. Friemel; John W. Goulding; Walter Hawkes; Ferdinand Holtkamp; Walter Holtkamp, Sr.; Walter Holtkamp, Jr.; Charles Litherland; Charles W. McManis; Martin Ott; Lawrence I. Phelps; Benjamin F. Sperbeck; Randall Wagner.

Source:

• The American Organist April 1989 (New York: American Guild of Organists), 75.
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Under the leadership of Walter Holtkamp, Sr. established a reputation for quality instruments of a unique incarnation of the ideals of the post-orchestral organ reform movement. Following a pattern established during the pre-World War II years, the firm uses only "Holtkamp" on nameplates and nameboards.

Source:

External Link: Holtkamp Organ Co.