Been a good season for unused vintage machines. Just the ones I'm remembering: yours, late Easy twin, Speed Queen twin. Styling suggests late/latest Duo. Congrats.
It is an electric condenser model. John has a similar TOL Hi-Speed condenser model in Beltsville. It has the larger door on top for the lint screen as well as detergent. It also has the dispensers where the user sets the amount of bleach and fabric softener on the control panel and warm air displaces that amount and sends it up to be added to the cylinder at the proper times.
This model does not have the fan for air circulation during the drying which is why it does not have a lint screen. A Mint In Box Duomatic is quite a find. You must be on Santa's nice list.