These sketch books and notebooks were acquired by the Fitzwilliam Museum, Cambridge in 1864, when the museum purchased Col. W. M. Leake's collection of ancient Greek and Roman coins, gems, vases and bronzes, together with his books and papers . Koehler had been Leake's commanding officer in the Royal Artillery while stationed at Istanbul in 1799, and therefore this may be how his personal drawings and notes were subsumed into Leake's own papers.
Upon the formation of the Museum of Classcial Archaeology (MOCA) in 1884, which at that juncture separated from the Fitzwilliam, the Leake papers were physically retained by the former. The Leake (and thereby also the Koehler) papers are now on long term loan to MOCA, inventory reference MOCA 2019:1. The collection's custodial care and cataolgue is provided by the Faculty of Classics Archives which has assigned reference codes in common with other archival holdings in the repository, in order to facilitate intellectual access to the material.