The manuscript is attributed to E.R. Jewett, but the accuracy of this claim is far from certain -- the only signatures with the Jewett name are written in pencil along the margin of a page, and don't seem to match the rest of the handwriting. Who E.R. Jewett was is also unclear -- there was a businessman in Buffalo named Elam R. Jewett, who owned a publishing company and engraving business; this E.R. Jewett, however, appears to have been born around 1811, much later than the date of this manuscript. Could there have been an earlier E.R. Jewett, who travelled around the Sandusky Bay in 1787? Or was this phrase book written by someone else (whose name we do not know), but later owned by E.R. Jewett of Buffalo? Or is there another explanation? (Anybody out there looking for a research project?)
Also, some of you might be wondering, "How could this manuscript be marked 'Sandusky, 1787' when we know that the city of Sandusky was not founded until 1818?" In fact, in that era most of the region around Sandusky Bay and along the Sandusky River was identified simply as "Sandusky." It is possible (or even likely) that this phrase book was written in or around what is now known as the city of Fremont, which was called Lower Sandusky until 1849, and was the site of a Wyandot village in the 18th century. (The city named Upper Sandusky -- farther up the Sandusky River -- still exists, of course.) For those who study Native American languages and cultures, and the early interactions between those peoples and the European settlers, this document may prove an invaluable resource. Although access to the original item is restricted due to its age and fragility, the entire document (21 leaves on 32 digital images) is available in digital format at the library.
Update: Oops. . . . I forgot about the Reverend Edward R. Jewett, who was a founder of the Bethel Church on Water Street (between Decatur and Jackson) in Sandusky in 1852. The image below shows Reverend Jewett some thirty years later. So we might be able to assume that the phrase book was in the Reverend Jewett's possession at some point, but we still do not know the complete provenance of this document.