"As an alternative to wire roof covers Symes produces cladding in 4mm and 6mm soft plate as a second skin. Twenty five sets produced and all but two shipped to France but never fitted." (Devils Chariots.p137)
The secondary plating necessitated fitting of extra studs for armour. As C company's tanks were fitted with the wire netting the second skin was presumably intended for D company tanks?
So far I've only come across a photo of 548 D13 "Delilah" with the spacer bolts in France; but all the Gaza females are photographed with them.
Were spacer bolts fitted in the Factory? If so were they fitted to tanks as they were produced , i.e. to a dozen females including 548 and a dozen males built about the same time (August 1916)?
Has anybody come across photographs of Mk Is with the Spacer bolts fitted other than those mentioned above?
Burster plates are also mentioned in David Fletcher's New Vanguard on the Marks I-III. IIRC they were to give additional protection against shell fire rather than acting as anti-grenade nets, so their issue may not have been linked to D Company. I'll have another look at the book tonight to see what the text says about them.