This oldy is among the oldest armed naval ships in the world. Former US navy destroyer escort nowadays in use as a training vessel in the Mexican navy.
ex USN Hurst DE250 commissioned 30 Aug.1943, transferred to Mexico 1 Oct.1973.
Other old armed navy vessels are. Paraguayan river gunboat PARAGUAY commissioned May 1931 (but no longer able to use the engines), patrol vessel ex tug CAPITAN CABRAL comm.1908, several times modernized but one of the most active vessels in that navy, Brazilian river monitor PARNAIBA comm.6 Nov.1938, also modernized and very active.
Peru has 2 British built river gunboats, AMAZONAS and LORETO commissioned durig 1935.
While North Korea is reported still using a former Russian Tral class fleet minesweeper, built during the 30-ties, now in use for patrol duties.
Also some countries have WW2 built former US Coast Guard buoy tenders in use as patrol vessels like Nigeria, Ghana, Panama, Dominican Republic, El Salvador and Colombia.