[aaron5]

At first I smirked when I read your American bit... but then I wondered... what if those were design choices?

For example, what if someone figured out the average sit-time of gasoline in the jerrycan, the average fault rate and leak rate of the lesser seam, and the average production time and lifespan of the jerrycan - then decided the sometimes leakier version was better because it was lighter, more quickly manufactured, etc?

And then perhaps American soldiers were more likely to pilfer gasoline for joy-rides or bartering, or to steal and sell the jerrycans themselves to their liberated friends and lovers, or for some other reason these cans were more likely to be "lost" as the Wikipedia article vaguely mentions - thus, make the can useless without the spanner and funnel, so as to make it a little less tempting for an improper owner to run off with?

Maybe?

Just thinking out loud.

But these questions reminded me just how fascinating everyday objects can be.

[jdkee]

I highly recommend:

https://www.goodreads.com/book/show/130748.The_Pencil

for a fascinating look at a universals object. Petroski's other books are quite insightful and illuminating as well.