From November 1922 "Commercial America"

The Orr & Sembower Company was located in Reading, PA and Chicago, IL, and a branch in Boston, MA. They were known to have manufactured portable steam engines. These engines were built in sizes 6, 15, 20, 25, 30, and 40 H.P.

Orr & Sembower were in business in 1888, building vertical hoisting engines. They had 175 employees by 1891. The company is no longer active and we have not found reliable data points for the company after 1974.

David Richard's Old Steam Powered Machine Shop YouTube channel features an Orr & Sembower steam engine.

Information Sources:

• Norbeck, Jack, Encyclopedia of American Steam Traction Engines, Crestline Publishing Inc, Glen Ellyn, Illinois, Pg. 44
• American Steam Engine Builders: 1800-1900 by Kenneth L. Cope, 2006 page 176
• Catalog of Copyright Entries. Third Series: 1956 lists some publications from Orr & Sembower, Inc., including a manual and a bulletin, both for the "Dryalator low-cost automated drying system" and both dated 15Aug56.
• A 1969 issue of Domestic Engineering has the following snippet.

  Mergers & Expansions—A major move involving three boiler builders has established Orr & Sembower of Pa. as “one of the largest international manufacturers of commercial-industrial boilers and bumers.” According to concurrently released ... will operated as Orr & Sembower with combined annual sales over $12 million. Russell Westover, president of Ray Burner, was named president of Orr & Sembower.

• A web page at the Pension Benefit Guaranty Corporation says that the Orr & Sembower, Inc.'s salaried-employee pension plan was terminated on December 31, 1974.