This is a river gunboat of the second half of the XX century. Peruvian Navy CF-13 Marañon, built by Thornycroft in 1951, she and her sister CF-14 crossed the Atlantic under their own power, in spite of a shallow draught of 7 ft. It is based at Iquitos.
Credits: Darth Panda´s riverine fleet, of course
PS: The pilothouse atop the superstructure looks odd and the glass looks very plain (not of the armoured type).