Thirteen envelopes unmatched to letters in the collection.

Five envelopes are from Henry P. McCahill, being addressed to "Miss Grace D. Gillson" at either Box 222 or Box 302 in Rockland, Maine. Four of these are postmarked at Washington, D.C., but the dates are obscured or torn away. Four envelopes are from John Porcius Gage, all addressed to "Miss Grace D. Nichols, Rockland, Maine." One is postmarked at Carversville, May 15 [likely 1866] and does not match a letter date. Two others are postmarked at Vineland but the dates are not legible; the final bears no postmark, it and the stamp having been cut out.

Two of the remaining envelopes are postmarked illegibly: these are addressed to "Miss Grace Nichols, Rockland, Maine," and "Miss Grace D. Nichols, Rockland, Maine."

Two of the envelopes bear no postmark: these are addressed to "Miss Grace D. Nicholls, Rockland Maine" [this is likely from Robert Rankin, as he frequently spelled Nichols with two l's]; and to "Mrs & Mrs John T. Robbins."