It's not the Crimea, the men are armed with Martini Henry rifles and are wearing the 1871 pattern infantry equipment? However I think the artist has based this on the well know Crimean War painting of the wounded man of the 42nd with comrade standing guard.
As the Black Watch and Seaforths were both involved in the action at Tel El Kebir and the later Sudan campaign, I can only surmise that this is what it is meant to represent. Both regiments wore their scarlet jackets [But not the doublet as shown in the window] during the action and were equipped with Martini's and 1871 Equipment, but not the feather bonnet, a bit of artistic licence on the part of the artist perhaps. I think this shows that the window must date from the 1880's.