British WWI Helmet With Camouflage Cover & Formation Sign

Brodies with a nice complete third pattern liner is fitted with a faded khaki field camouflage cover painted with a red inverted triangle formation sign on one side.  The cover is stretched taut over the crown, exhibiting rust stains from prolonged close contact with the helmet and some minor worn / weak spots along the edge.  Without unduly disturbing this relationship, I have gently loosened it just enough to get a small pen light in to see if there was a matching painted formation sign on the helmet side (there is not).  

Per the Kevin Beckhurst reference, this formation sign could actually apply to a few different units over time, but assuming the helmet with the 3rd pattern liner is original to the cover, which very much appears to be the case, the precludes some earlier uses of the insignia and leads to the conclusion that this designates 12th Battalion, Cheshire Regiment.  $1000-$1500