MRB — Manufacturing Record Book
The compiled evidence pack handed to the client at the end of a fabrication contract, proving that what was built was built as specified.
An MRB gathers, in the order the contract requires, everything that shows the job was done to specification: material certificates, welding procedures and qualifications, examination reports, heat treatment records, dimensional reports, nonconformances and their disposition, and the release documentation.
MRB or MDR?
The two terms are used interchangeably often enough that arguing about them wastes time. Where a distinction is drawn, MRB leans toward the manufacturing evidence for a fabricated item, and MDR — Manufacturing Data Report, or Manufacturing Data Record — toward the wider documentation package for delivered equipment, including design and operational documents.
What matters commercially is not the acronym but the index: the client’s required contents list decides what the pack is, whatever it is called.
Why it is the expensive part
Because it is compiled at the end, from evidence produced continuously over months. The work is real and it is unbillable, and it lands in the fortnight when the margin on the job is already fixed.