Old vintage Oil Operators booklet by Pacific Valve Inc.! The first section is 225 pages of "Oil Operators", the second section is for "Drilling Contractors", the third section lists "Oil Sales & Service Firms", the last section lists "California Consultants and Agencies". Used condition, with edge tears, marks, notations, etc. 414 pages total, 3.2 x 6.2 inches. Estimated date is around the 1940's or 1950's.