Proper census. Information gathered by each local Police station of the time.
To date censuses have been taken in 1926, 1936, 1946, 1951, 1956, 1961, 1966, 1971, 1979 or at least thats what gov says and the dates agree with 1936 and the recorded age of everyone here at the time.
I am at a little of a loss as there seems to be some daft thing about 100 yrs and I know that this information is not due for release untill 2036 but my father says there a only a few survivors noted within the details and for the life of me I cnat see anything that would cause a problem or at least not to anyone involved in this posting.
As to why it is in my posetion is a long story but the short version is simple. Portglenone Barracks threw it in the skip.