This is one of a set of contract drawings consisting of 3No. plans and 3No. Elevations. (Drawings GUA BUL 6/3/1 to GUA BUL 6/3/6 inclusive.) This item includes a pencil note on the drawing - possibly by the builder - requesting Drawing "Revised Plan No.19".
The drawing, or perhaps the list of Contract signatories is initialled by "A. T."