Gives 79 as age in 1911 census = Date of Birth of 1832.  

General Registry Office has Death certificate for James Gray of Managher, died 1912, aged 80, Present at Death was daughter, Eliza Jane Gray.  This must be this James, even though he seems to have moved to Managher in the last year of his life, because his daughter, Eliza Jane, is unmarried in the 1911 census and he is aged 79 at that time.  There is a problem with the Griffiths Valuation Revision Book which seems to show James arriving in Managher in 1913 and scratched out in 1915 when he is replaced by Eliza Jane, who, herself, is scratched out in the same year, 1915.  But this is probably explainable by the way in which the Griffiths Valuation Revision Books are kept.

Gives 79 as age in 1911 census = Date of Birth of 1832.  

Death Index in General Registry Office, Belfast, shows death of Rachel Gray in 1919, aged 87 = Date of Death of 1832 again.  Death Register entry shows: died 25th March 1919 in Managher, a widow, aged 87, a labourer's widow, of old age certified.  A David Lawrence, son-in-law, of Ballylagan, was Present at Death.

Gives age as 55 in 1911 census = 1856. 

Still alive by 1912 when she was Present at Death of her father in Managher.

Title : Miss Date of Death : 5 December 1937
Surname : Gray Date of Grant : 4 March 1938
Forename : Eliza Reseal Date : 
Registry : Londonderry Effects : Effects £1194 16s 5d 
No Image
Full Abstract :
Gray Eliza of Glenhall county Londonderry spinster died 5 December 1937 Probate Londonderry 4 March to James Gray and John Jamieson farmers. Effects £1194 16s. 5d.

SUSANA GRAY
Pedigree
  Female

Event(s):
Birth:
25 AUG 1865  0434, Aghadowey, Londonderry, Ireland
Christening:
Death:
Burial:

Parents:
  Father: JAMES GRAY
Family
  Mother: RACHEL MITCHELL  

Date of Birth Source: International Genealogical Index.  

Death Index shows a James Gray died aged O in same year, 1871.  This man cannot be alive after 1911 if the 1911 census is correct.  It shows that his mother, Rachel Mitchell Gray, had four children, only two still alive.  One of these was Eliza Jane who was living with them at this time and the other one was the female who must have been married to the "David Lawrence, son-in-law" who was Present at Death at Rachel's death in 1919.