If you are not familiar with FindaGrave, it's a huge website of memorials which main purpose is to furnish information about a person's death and place of burial.Most of the memorials are created by just ordinary people, but the U.S. Veterans Affairs and the American Battle Monuments Commission have also added thousands of military graves.This is one of them.
There's no way to know now if this Robert Carlton was your grandfather, but he certainly is a good possibility.The name is correct; he was in the navy; and since he was born in 1898, he would have served in World War I.I assume that "AS" stands for "apprentice seaman."
I tried to find him in other records, but unfortunately I didn't find much.I couldn't find him in a census record at all, but maybe someone else can.I did find that his funeral was briefly announced in the Portland newspaper OREGONIAN on five different days, December 29 & 31, January 1, 2 & 3.All it ever said though was
"Carlton--Robert C.Service 10:30 am Friday at BATES SOUTHGATE CHAPEL 10305 SE 82nd ave. Private committal Willamette National Cemetery"
(from the 1 January 1969 issue, page 30).There was no obituary for him, but then, the paper had far fewer obituaries than funeral notices.
The Social Security Death Index does list him, and this is what anyone can see:
Name:Robert Carlton SSN:568-03-1484 Last Residence:97266Portland, Multnomah, Oregon, United States of America Born:20 May 1898 Died:Dec 1968 State (Year) SSN issued:California (Before 1951)
the website will explain some about Social Security cards.The original application, what you really want, was filled out by the person himself/herself, and it should include his/her full name and parents' names.These applications are not online though, rather you must send away and pay for a copy.
You also might want to locate an historical library or society in Portland.Maybe someone can look for his obituary in other newspapers.