The book has the following notation on page 90:
"DUNHAM, C.O., Rev., and wife, trans. to East Dover, Vt.; BC"
At the front of the book (pg v) under "Primary Sources" - "BC" is described under "Church Records" - as "Georgia Plains Baptist, 1893-1946".
No year given in the notation, but if you think this is "your" DUNHAM, at least you now have another placename.
Hope this helps... and good luck!