The Sir William Osler Collection, distinct from the Bibliotheca, is an extensive archival holding of Osler's correspondence (including eighteen hundred original letters), daybooks, accounts, engagement books, legal documents, book invoices, membership certificates, notebooks, lectures, addresses, newspaper clippings, photographs, books with manuscript additions, and miscellaneous loose items formerly inserted into individual books in his library. The collection also contains various family papers, including correspondence of Lady Grace Revere Osler and Edward Revere Osler.

Fonds consists of personal letters between Howard family members and close relations (C. P. Howard, William Osler, Grace Osler, the Wright family etc.). Subjects range from wedding engagement congratulations for C. P. Howard and Otillie Wright, personal introductions from Grace Osler, to professional appointment letters. There are original photographs (as well as a few copies) of candid Osler family moments, formal family portraits, hospital photos of Osler at work, as well as several professional portraits of William Osler by prominent Montreal photographers. The fonds also includes miscellaneous reprints, booklets, and various other publication materials such as R. P. Howard's valedictory addresses to several graduating classes, personal copies of medical case studies, Olser's handwritten medical notes from 1875-1878, as well as original caricature sketches by Edward Revere Osler. In addition, there is a small photo album (in its own presentation box) with John Hopkins Hospital staff portraits (names included) from 1902-1903. The photo album is stamped "C.P.H." on the front cover.\nIncluded in the fonds are the following books: The Holy Bible (Oxford, 1912), The Poems of Edgar Allan Poe (Diamond Edition, New York, 1881), and Robert Bridges The Spirit of Man (Longmans Green and Co., London, 1916).

Fonds documents the Mallochs' activities related to their medical and literary work. The fonds contains notes, correpondence, commonplace books, account books, material related to publications, family memorabilia, scrapbooks, photographs, telegrams, postcards and certificates.

All three, on black-edge stationery, undated. One has pencil note: "After Revere's death?" Another has date, "1920" pencilled in.