The collection consists of documents amassed by Roderick Mackenzie. Among the Masson manuscripts there are other series of letters; as well as journals kept by North-Westers and various business documents. Some of this material exists as originals; others are contemporary copies - the George Keith letters for example are contemporary copies on paper watermarked 1827. The collection also includes some duplicate texts - contemporary copies or later nineteenth-century copies that in some cases represent edited versions of the texts. Samuel Wilcocke's account of the death of Benjamin Frobisher exists in a draft original (or contemporary copy) and in a late nineteenth-century clean copy. Of course Benjamin Frobisher did not die in the dramatic circumstances as recorded by Wilcocke, but peacefully in Quebec City in 1821.

Series consists chiefly of 38 manuscripts related to the North West Company. Among the Masson manuscripts there are other series of letters; as well as journals kept by North-Westers and various business documents. Some of this material exists as originals; others are contemporary copies - the George Keith letters for example are contemporary copies on paper watermarked 1827. The collection also includes some duplicate texts - contemporary copies or later nineteenth-century copies that in some cases represent edited versions of the texts. Samuel Wilcocke's account of the death of Benjamin Frobisher exists in a draft original (or contemporary copy) and in a late nineteenth-century clean copy. Of course Benjamin Frobisher did not die in the dramatic circumstances as recorded by Wilcocke, but peacefully in Quebec City in 1821.