ID on Ammo boxes.

[Clive_Dakers]

B.166 I
Size: Length 19.8" Breadth 9.1" Depth 13"

Used for:
3 in M.L. Mortar HE
3 in M.L. Mortar Smoke
3 in M.L. Mortar Chemical
3 in M.L. Mortar Practice

Number Packed: 6
Gross weight: 88 lbs

Grenades No. 73

Number Packed: 10
Gross weight: 62 lbs

Grenade No. 77

Number Packed: 34
Gross weight: 41 lbs

Grenade No. 79

Number Packed: 24
Gross weight: 56 lbs

Portfires, common

Number Packed: 200
Gross weight: - lbs

Bombs, P.I.A.T., H.E.
Bombs, P.I.A.T., Inert, practice

B.166 II (your red box)
Size: Length n/k Breadth n/k Depth n/k

Used for:
Grenades, No. 73

Number Packed: 10 + 1 tube of 10 detonators
Gross weight: 62lb approx

C.255
Size: Length 25.1" Breadth 16.4" Depth 10.8"

Used for:
5.5-in. B.L. gun Cartridges Charge 4

Number Packed: 6
Gross weight: 99.5 lbs

C.298 is not in my reference, could be a Canadian box that wasn't used in British service.