You sure? How can the mashgiach be sure that what is in the tanker is milk of a cow and not from a horse, or even a goat? How does he know it isnt cloudy water or even soy milk? Surely there is more than just inspecting and sealing a tanker.
I mistakenly formatted my previous post as two paragraphs, it should be one paragraph.
Mods: can you fix post 441681?