- Prior to 1999 the Engineer designations were 12 series and 83 series.
- In 1999, CMF 83 changed to CMF 51.
- In 2004, CMF 51 changed to CMF 21.
- In 2004, the engineer designation changed from 12 to 21.
- In 2008, the engineer designation was changed again, from CMF 21 to CMF 12.
- In 2013, the engineer officer designations 12B (Combat Engineer) and 12D (Facilities/Contract Construction Management Engineer (FCCME)) were consolidated into 12A.
- 12A Engineer, General
- 120A Construction Engineer Technician
- 125D Geospatial Information Technician
- 12B Combat Engineer -
- 12C Bridge Crewmember
- 12D Diver
- 12G Quarrying Specialist
- 12H Construction Engineering Supervisor
- 12K Plumber
- 12M Firefighter
- 12N Horizontal Construction Engineer
- 12P Prime Power Production Specialist
- 12Q Power Line Distribution Specialist (RC)
- 12R Interior Electrician
- 12T Technical Engineer
- 12V Concrete and Asphalt Equipment Operator
- 12W Carpentry and Masonry Specialist
- 12X General Engineering Supervisor
- 12Y Geospatial Engineer
- 12Z Combat Engineering Senior Sergeant