faux black leather-covered binder with brass corner protectors, stamped to spine 'TECHNICAL INSTRUCTIONS B.B.C.' and to front cover 'TECHNICAL INSTRUCTIONS, THE BRITISH BROADCASTING CORPORATION', with label inside front cover which reads ' Copy 958, E.I.C London Control Room’, designed to be updated whereby early pages are removed and replaced with later pages, earliest part of the book is chapter 10 'TONE SOURCE TS/4' dated March 1935, latest chapter is chapter 12 'SCHEDULE of SMALL VALVES' dated July 1939’