Looks like 220 plug usually for an air conditioner or electric stove.

Thank you. It's in the primary bedroom, so an ac makes sense. Do they still make plugs like that now?

It appears to be a standard NEMA 10-20R 240 Vac non-locking receptacle (20 amperes), for which the NEMA 10-20P plug is used. These might be obtained at your local electrical distributors, manufactured by various companies such as Hubbell, some hardware stores, and on-line suppliers.

Hold on... what are you planning on plugging in to that? Are the rest of the receptacles in the house ungrounded?

Nice work pointing that out, @dennisgli. Older houses, such as mine before I massively modified it, had circuits without grounds. Older equipments, for me now limited to my Kenmore dryer, were operated with neutral as ground. In the case of the dryer, the motor and electronics are run from 120 Vac and grounded to the chassis, while the heater coils run off of 240 Vac. I haven't yet found time for determining whether I can successfully rewire the dryer to get neutral off of the chassis.

Some here may recognize that with neutral connected to the chassis, and the chassis connected to metal ducting, and the unbalanced 120 Vac load, any connection or even touching of the ducting to any ground path, such as a plumbing or heating pipe, will cause a ground fault proportional to the relative resistances between the neutral path to ground and the gratuitously grounded path to ground. Hence, upgrading to a GFCI breaker will be doomed until the neutral and chassis are properly isolated, as I discovered.

No, not trying to plug up anything currently. We're going to meet with a contractor at the house tomorrow for a look over (if it doesn't go under contract before then). I wouldn't know where to start to look to determine if things are grounded or not?

Does this help?

Yes, actually; thank you! Sounds like this may be a bigger undertaking than I originally thought for this house.