Arriving as a joint delivery with No. 4 Loch in 1874 in readiness for the opening of the Port Erin line, the locomotive is named from the Latin word meaning Isle of Man. Together with sister No. 4 she carried unusual nameplates to compensate for the injector overflow pipe which bisected it, thus the name appears "MO NA" with a gap to allow for the copper pipe; modifications to the layout leaving this feature redundant and giving it an unusual appearance, as can still be seen on sister locomotive No. 4 Loch which remains in regular traffic today.
 

As with the other fleet members, she has idiocynracies that distinguish her, such as a chimney numeral in a slightly different style to the other locomotives. The locomotive also carried brass "5" numerals on the side tanks about the name plates, though the drivers' (left) side one was removed latterly. Also of note is the horizontal grab rail on the rear cab sheet, that curves at each end, whereas all others have straight ends. No. 5 was a regular on the Peel Line later in her career and remained in service right until the 1970 season when she refused to hold a head of steam and was subsequently mothballed. Stored in the open on display at Port Erin until 1974 when it was returned for storage in the carriage shed at Douglas Station, it was here, together with No. 6 Peveril, that the locomotive remained until 1998.
 

She was privately purchased from the newly-nationalised railway in 1978 by the Isle of Man Railway Society but remained on site, being stored in the carriage shed at Douglas until it was demolished to make way for new bus garage and offices in 1998. The owners changed name to the Isle of Man Railways and Tramways Preservation Society some years later, but carried out no further work to the locomotive until it returned to the custodianship of the railway.
 

Currently in the back of the new carriage shed and hermetically sealed, No. 5 has had no attention for many years and is a sorry sight, still wearing her 1967 spring green livery, now very faded. She was one of two (the other being No. 12) to carry a brass fleet numeral on the left-hand tank only, though No. 12 carried (and carries) them on both sides. In 2008, to mark the 40th anniversary of the closure of the railway, sister locomotive No. 10 was cosmetically renovated for a short period to resemble No. 5 in an attempt to recreate the last ever train from Peel to Douglas on 5th September 1968. Due to asbestos present in the locomotive's lagging it was hermetically sealed in 2009 and remains out of bounds.  In April 2012 an agreement was signed which saw this locomotive return to railway ownership.