What type of key switch though?

https://unitednuclear.com/fun-scientific-stuff-c-28_54/antimatter-hazmat-sticker-p-1118.html

Something like this?

In the US it would just be for the compressed refrigeration gasses (if any), likely 2-1963. If you felt cheeky you might have a Class 7 plaquard (radiation) too, but you'd probably get in trouble for incorrectly labeling your cargo since 100 anti-protons isn't exactly a radiological threat.

Everyone is saying no, I want to explain why.

Black holes are a gravitational phenomenon. Basically too much mass in too small of an area distorts spacetime so heavily it prevents even light from escaping, though it does emit hawking radiation.

Antimatter is on the other hand a concept relating to a different fundamental force: electroweak interaction. Antimatter can be summed up as matter with the opposite charge. In an anti carbon 6 you'll find six anti protons (negatively charged particles the same size as protons and made of antiquarks), six anti neutrons (neutrons made of antiquarks), and orbiting around it will be six positrons (basically electrons but positive). It will have the exact same mass as a regular C^6.

Antimatter is relatively common these days, being produced in most major hospitals to be used as part of PET scans. It can be weaponized in theory, but volatility and volume to cost and transportability say it's unlikely to ever actually be used that way. This is risking an explosion of less force than a toddler's punch. And even an antimatter bomb big enough to send the earth to simultaneously collide with mars and Venus wouldn't open a black hole in it's explosion because explosions are in a force body sense, the opposite of a black hole. These things can feel mysterious and magical, but like everything else they're just physical manifestations of the math and physics our universe operates under

Not even close.

No.

All black holes are portable, if you have the right equipment.