Your badge is undoubtedly of WW2 vintage and appears in my book
Doing Their Bit; Home Front Lapel Badges 1939-1945 as illustration D14 in the chapter which explains the purpose of On War Service and National Service Badges.
Sadly like many such wartime badges it has not so far been possible to decipher the meaning of PTF although MFG clearly stands for Manufacturing.
No such firm appears on the Graces Guide website
http://www.gracesguide.co.uk/Main_Page which is a useful tool for tracking down defunct British companies.
I'd be delighted if someone could identify this firm.
Jon