Sentinel number 753 was made by engineers Alley and MacLellan in Glasgow in 1914. It is the oldest Sentinel in existence and the only surviving Scottish built Sentinel waggon.
In 1905 Alley and MacLellan began to make steam wagons and soon captured a large share of the market with their undertype standard 4 ton waggon.
This Sentinel was sold new to Alexander Runcie, Carrier of Inverurie and spent its working life in the locality. By 1945 it was working with McIntosh of Forgue's haulage fleet near Huntly and eventually was recovered from their yard, partly dismantled, in 1966 for preservation.
'Standard' Sentinels were remarkably simple and robust steam waggons that featured an efficient vertical boiler whose steam generating capacity, in the hands of an experienced fireman, gave the vehicle its advantage over its competitors. The small boiler ran at a relatively high pressure, 230 psi, and delivered superheated steam to the eight valve twin cylinder engine.
To aid efficiency, exhaust steam preheated the boiler feed water to close to boiling in normal running conditions. Standard waggons were generally used with a trailer, enabling them to move loads of around 10 tons.