1930, 379grt
Cook, Welton & Gemmell, Beverley (539) as KINGSTON OLIVINE H209
Lengthened at Smiths Dock 1937
8/39-5/42 served as Royal Navy anti-submarine trawler FY.193
1942 KINGSTON OLIVINE H209
1947 LANGLAND BAY SA72
1954 MASONA FD16
Broken up at Troon 11/1956
seen here in wartime guise

The KO ship, anti submarine trawler Kingston Olivine, photo apparently dated 1 April 1944.
This is 1 of a few images of KO widely available, IWM A22672, with IWM A22673 shows the stbd side, whilst others include crew members.
In fact she is flying her pendant number, which is not painted up, FY 193, off her fore mast, flags from our left,
1 - Fishery pendant, i think, blue & Yellow.
2 - Numeral 1, red & white.
3 - Numeral 9, red & white.
4 - Numeral 3, blue & yellow.
The large KO is a feature a number of trawlers and such like had painted up, in the latter parts of the war, i believe.
Would be nice to know who, why, when, this system was approved, as it is very logical and effective, even though using only 2 letters will give you 676 vessels so marked. I have seen a few with 3 letters, which extends the system somewhat.