Original oil and gas trade magazine vintage ad for SCHLUMBERGER WELL SURVEYING CORPORATION. Johnston Testers. Main office was located was located in Houston, Texas. Also located in Los Angeles, California and Calgary, Alberta, Canada. First in DST Drill Stem Testing. Article titled Five Important Points of D.S.T. Pressure Charts by Glenn Taliaferro. He was the Manager of Chart Department, at Johnston Testers, in Houston, Texas. His photograph is shown. This unique 1957 old petroleum oilfield services magazine advertisement would display beautifully matted and framed.