Hi. Both receptacles below are rated 20 Amperes for USA :
This one does not accept a typical plug :


This one does :


What appliances have plugs for these outlets ? Never seen a vacuum cleaner, microwave oven, coffee maker, clothes iron, clotheswasher... equipped with such. What are they meant for on a dwelling with these wired to a 20A circuit breaker ?
And the reverse; if you install a 20A circuit breaker with these receptacles above and AWG12 wiring... What is their typical usage ?

 

My 240-volt space heater uses the upper outlet.

 

The top one is for 240 VAC. The two horizontal slots are for 15 A plugs and the vertical and horizontal slots are for 20 A plugs.

The bottom one is for 120 VAC. The two vertical slots are for 15 A plugs and the vertical and horizontal slots are for 20 A plugs.

 

Big 240 volt air conditioners use that 20 amp 240 volt plug.