Home / For Sale / Archived / 7 1/4 Wren 0-4-0 7 1/4 Wren 0-4-0 SOLD Description Description Wren is an 0-4-0 Saddle-Tank locomotive in 7 1/4″ gauge, designed by Ken Swan and has Hackworth Valve gear. Kerr Stuart & Co built 167 of the prototype 2ft gauge locomotives for industrial use around the globe.