Its the angle as it's as thick as all the otherMk IIIs I've seen and its a perfect fit in the case, not too tight but no rattling about. This case has no markings on it at all hence the conclusion its a modern civy job. It has a roll buckle to close the case and to adjust the strap lenght. but the latest ones have press stud closure.

The compass has this on the base

CKC/C
Arrow mark
16978C
MK.III
1943

The one that the boys have inherited is smaller and much thinner and isn't liquid filled has this on the base.

Inverted broard arrow
F-L:
No. 87966
1917

On this vague note a distant relation of the wife has dumped some bits on us with instructions to eBay and buy the kids something and included are her husbands dads Great War era Binos. On the front plate is a large broard arrow and on the left back plate thngy near the eye piece

Binocular Prismatic No 3 Mk I
Magnification 6
No 62152 (it fades out, not sure about the last number.)

on the right back plate is
A. KERSHAW & SON LTD
LEEDS
1918

Which was the year he was commisioned after serving as a private in the Artists Rifles i think. We got a wad of documents, training notes and Officer type bumpf with them.

ATB

Tom