Workbook, combined volumes 12 & 13, compiled by J. H. B. Chapman

A Department of Naval Construction workbook, combined volumes 12 & 13, compiled by J. H. B. Chapman. Officer Number 294.

The workbook lists two volume numbers (below), but it is likely they really represent just one volume of work.
Workbook No 294/12 - Admiralty Collection
Workbook No 294/13 - by J.H.B.Chapman