The series comes from the 'Current Employment Statistics (Establishment Survey)'
The source code is: CES3000000004
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Average Weekly Overtime Hours of All Employees: Manufacturing [CES3000000004], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/CES3000000004/, September 3, 2015.