Source, aged 77 at death in 1879.

SS: Finally found John's obit Coleraine Chronicle Saturday 2/22/1879
Feb. 15,1879 Finlay at his residence Long Commons Coleraine John (late of Ballystrone, Dunboe) farmer, aged 77.
Enjoyed our day in Coleraine. I left my Finlay stone in your car. Please save until next I return.
Will be in touch soon.
Sue

Name    JOHN FINLAY
Year of Death    1879
Group Registration ID    6942083
SR District/Reg Area    Coleraine
Deceased Age at Death    77
Image
John Finlay died 18/02/1879, age 77, Commoms, Coleraine, married, farmer, bronchitis 1 month, uncertified, no medical attendant, Elizabeth Finlay, Commons, present at death signed x mark

Could this be him in the LDS Pilot:
Name: Samuel Finlay
Registration district: Coleraine
Record type: DEATHS
Registration date - quarter and year: Oct - Dec 1879
Estimated birth year: 1806
Age: 73
Mother's surnames:
Film number: 101589
Volume: 1
Page: 369
Digital GS number: 4200221
Image number: 00559
Collection: Ireland, Civil Registration Indexes 1845-1958