OQF 6 pdr 7 cwt

[tankbarrell]

The British and Canadian box does not have a hole through the bottom, there are two inner shelves, the hole you see is through the lower shelf.

The British manual specifies items that go in the box but it only lists the 'box, spare springs and pins CM98'. There is nothing listed that would fit in the circular holes. It is clearly for something though, it is too complicated to not be for something specific!