Map referencing Query

[TEW]

I have a few trench maps (57D NE 4) for the Achiet le Petit, Miraumont area, trenches corrected to 7/3/1917. Hopefully, there is part of it displayed here. Well at least it did upload but I can't see it in the preview post!!

Just to the west of Achiet le Petit there is an emboldened northing which separates Letter prefixes L and G. The squares abutting this northing only have 2 sub-squares instead of the usual 4, i.e. a,b,c,d.

As there is only a northern and a southern square what should the convention be for a map reference for L.24? Is the southern square C or B?

The reason I ask is that I have Information relating to activities in these squares either from 187^th Inf. Bde Summary of Intelligence 2/3/1917 or from Officer Commanding B Coy. 2/5^th KOYLI’s Field Message Army Form pads C 2121 and Battalion Ops. Orders that use an odd combination of map references.

I have references to squares; G.19.d.5.5., G.19.c.1.1., G.19.a.9.5., G.13.b.5.5 and L.18.c.6.7 as they relate to locations of snipers and forming up lines as well as positions to establish posts it would seem quite important to understand the system but clearly not everyone did.

Any suggestions gratefully received

TW