William Giles Royal Marine

"Crimean Veterans Funeral. CATFORD RESIDENTS- 21 YEARS SERVICE IN MARINES. The funeral took place on Friday of Mr. William Giles, a Crimean veteren  who died at 143 Brookdale road, Catford at ths age of 85.
A native of Plymouth, he  joined the Royal Marines on April 13th 1854 15 days after England and France declared war on Russia. He saw a good deal of the fighting and afterwards served during the Mutiny in India and in the China and Zulu wars. He held four medals and one in recognition of meritorious service.
When he took discharge from the Royal Marines (in 1875), his record was one of exemplary service and he retired with the rank of colour sergeant. He was, premoted to Corporal in November 1861, Sergeant in December 1866  and Colour Sergeant in 1873. The ships he served it included the Cornwallis and Royal George.
After leaving the Marines be was appointed as an inspector of the parkkeepers at Greenswich Park. and served there for 26 years. He was twice married and is survided by four sons and two daughters. One of his sons. while with the 20th London in France in 1917. was taken prisoner  and spent 10 months in a German internmant camp
As stated Mr Giles was buried on Friday The coffin wrapped in a Union Jack was conveyed on a gun carraige to Shooters Hill Cemetery where the internment took place. A bearer party and bugler from Woolwich were present and accorded military honours"

Sydenham, Forest Hill & Penge Gazette - Friday 14 January 1921

Not sure how he got the SAGS medal if he left the Marines in 1875 N/T in Duttons in the Naval Section
All I can think of is if he re enlisted in another Regiment or went as a volunteer but his service as a park keeper seems to suggest otherwise.