A two part question:
Were there ever real bombs shaped like a ball or orb with a long wick coming out of the side?
Was alcohol ever available and/or distributed in jugs marked “XXX”?
Was flour ever distributed in giant sacks marked “XXX”?
“Google is your friend!” Yeah, you go do a Google image search for “bombs wicks” or “XXX jugs” from work.
The round bomb thing is based on cannon balls, many of which were hollow and could be filled with explosives.
No idea on the other questions.
The globe bomb was a hand grenade-type device used by anarchists in the late 1800’s:
Three parts, really. I added the flour.
Hell I MADE one of those at work!
Yea it was made out of a hamster ball and we put a tiny fogger in it to make it smoke, but it was still cool.
You try finding a supplier for liquid latex at work. That was an interesting day.
For what it is worth, Wikipedia says moonshiners supposedly put an “X” on the jug each time the contents went through the still. (I say “supposedly” because Wikipedia doesn’t put forth the idea as an absolute fact.)
The SDSAB doesn’t have much to offer on the XXX/alcohol connection, either. LINK
Grenadiers used the bomb thingies-there was a guy in the POTC movies who used them.
And when we die, do our tongues hang out, and do our eyes become Xs? 
I saw a show on Discovery about alcohol and the X’s indicated the proof.
But why always three? Why not two or four? And … was the X system really ever used? What about flour?
BTW, thanks for the answer about the bomb! Were those types of bombs really common?
Actually, they were putting their mark on it, but since they were using X, they signed it a couple of times just to make sure you knew who was signing it. Thank you, I’ll be here all night.
On a more serious note:
http://running_on_alcohol.tripod.com/id6.html
Don’t know how reliable that site is, but it seemed to discuss what you were asking about.
http://www.pivonka.net/jnpteeninUS.html
Also don’t know about that site, but seems pretty reasonable.
XXX Brand flour and alcohol used by cartoon cathouses everywhere.
You are missing an X - Castlemaine XXXX - certainly alcoholic.
Of course, it sets up the line beloved of Kiwis everywhere.
Why do Aussie breweries sell XXXX?
cause diggers can’t spell beer 
Si
For beer, there’s also Dos Equis (“Two X’s”), though, if Wikipedia can be trusted, it was originally named XX Century Beer (in Spanish), so the XX is of recent origin and unrelated to XXX on moonshine or flour or other comestibles.
We’ve established that globe bombs existed, even though they probably weren’t that common. Same thing with flour bags marked “XXXX”. What about jugs of liquor, though? The X’s supposedly identify the number of times the alcohol was distilled, but were they ever really used, unironically, to mark jugs of booze?
Not an authoritative cite, but when I saw Master and Commander, they had a stack of bombs in one scene that looked exactly like the cartoon bombs.
Hmmm . . . since we’re doing old cartoon conventions, I hope no one minds if I tack on a question:
And has anyone ever worn a lampshade on their head at a party (without irony)?
And has any housewife ever attacked her husband with a rolling pin?
Probably potassium aluminium sulfate (alum is a generic term for these sorts of aluminium sulphate salts). It is an astringent, and causes blood vessels to shrink. Styptic pencils containing alum are used to stop shaving cuts bleeding - but sting like buggery. I’ll stick to little bits of toilet paper .
It is also used in pickling - maybe leading to the shrunken (pickled) head analogy.
Si