Manufacture of machinery and prime movers other than electrical equipment. Included are agricultural and industrial tractors and conveyors; refrigerators; exhaust, ventilating and air conditioning units; sewing and washing machines; office machinery, such as typewriters, calculators, cash registers and accounting equipment. To include also machine shops engaged in producing and repairing machine and equipment parts and the production of ball bearings and machinists' and other mechanical precision measuring instruments. The manufacture of automobile, aircraft and marine engines and other specialized parts is classified in the appropriate group of major group 38 (Manufacture of transport equipment).