Matthew Boulton, William Matthews; Charlotte Matthews, 1770-1791.

This file is mentioned in the "Catalogue of Papers, M. B.’s Counting Room, 1760 to 1790," compiled by William D. Brown about 1791, under the title:
Wm. Matthews [Letters] 1770 to 1790
The latter date apparently refers to the year most recently completed when the Catalogue was made. Several of the documents in this file were redocketed by Brown, probably at the same time. When M. R. Boulton re-arranged his own and his father’s papers, about 1819, the contents of the file were transferred to a portfolio, the title of which (according to the Inventory compiled by the Assay Office in 1921) was:
W. Matthews 1770 to 1791
Under the same arrangement the portfolio was placed in Box K. II ("Special Correspondents—Partners and Agents"), though by the time it arrived at the Assay Office it had been moved (presumably without reason) to Box M. III. Unfortunately, the portfolio appears to have been discarded. It will be noted that the title of the file has now been altered to take account of the number and importance of the letters from Matthews’ wife Charlotte.
14 was evidently returned to Boulton by Matthews at some unknown time. 15, 88, and 92 were transferred to this file by the Assay Office after it was originally listed, but their origins are not known.