Saw in 1930 Home

I saw this outlet in a 1930’s home in N.C. does anyone know what type of outlet this is? The basement was recently finished and this plug looks fairly new.

20 amp, 240v receptacle.

Read the numbers on the outlet…

Common for window A/C.

I agree it’s a 240 volt 20 amp receptacle. It can also accept a 240 volt 15 amp plug hence the T slot. Just a suggestion, it’s a receptacle outlet or a receptacle it’s not a plug.

NEMA has charts available to help identify the various configuration by ampacity and voltage.

NEMA Straight Blade Reference Chart

Thanks all so much