The 1913 Handbook placed the Fuze Indicators as one behind the Gun Shield, and another on top and to the rear of the Ammunition Wagon.
It appears that the Indicator had a transformation near the beginning of ww1, from a large ‘Clock’ to a ‘Slide Rule’, which became Indicator Mk11 …. this made all the original Indicators – Mk1’s.#
This had me wondering when in time were the obvious ( Mk 11? ) ‘Indicator’ brackets placed on the Wagon’s upper rear door,- and ‘found’ in the Amendments 1914/15 the instructions for the locations for the Mk11 Indicator, - behind and top right of the Gun Shield ( as the Carragh Camp Museum Gun -
https://www.youtube.com/watch?v=0mQ5oGqYHco&t=544s ), ), and at the rear of the Ammunition Wagon.
So mid/late ww1 production Wagons had the Brackets installed…….