The summary of the proposition as it appeared on the general election ballot: Do you want to require background checks prior to the sale or transfer of firearms between individuals
not licensed as firearms dealers, with failure to do so punishable by law, and with some exceptions for
family members, hunting, self-defense, lawful competitions, and shooting range activity?
Information on the language of the proposition is from the Official Voter Information Guide issued by the Maine Secretary of State: https://www1.maine.gov/sos/cec/elec/upcoming/citizensguide2016.pdf
A total of 3798 votes were cast by citizens abroad; 3178 in favor and 620 against. The state of Maine does not tabulate these votes by county.
Source for Popular Vote data: Maine Secretary of State. 2016 Election Results, Maine Secretary of State (http://www.maine.gov/sos/cec/elec/results/2016/referendum16.xlsx) (accessed 11 Dec 2017)