25 pounder base ejection smoke

[earni74]

A friend has a sectioned 25 Pdr B.E Smoke with 3 smoke pots inside (all inert) but now he has a larger smoke pot which will take 2 in the shell, the larger smoke pot is stamped No7 mk1 whereas the 3 pot ones are stamped No3, can anyone help

 

[earni74]

My friend has revealed that the smoke pot is for the 3inch smoke B.E Mortar