There are 3 John Sullivans born 1885/1886 in Monmouth, none on 11 Aug, and none with a second Christian name "C"
1885 Aug 11 Born Monmouth
1920 Nov 22. Joined with RIC no 75370 & ADRIC no 198 . ex -Soldier & warehouseman
1920 Dec 2. Posted Mayo
1921 Oct 30 to 30 Nov on Leave
1939 Regiser has a number of plain John Sullivan in Monmouthshire, none have right dob