This is a reflector oven or tin kitchen as it was often called. They were used in the 18th and 19th Century for cooking meals in front of the fireplace. A goose or chicken was placed on the spit and rotated periodically to cook . The window in the backside was to baste the meat as it dripped onto the base of the oven which has a catch basin and a spout so you could pour the drippings into a pot to make gravy.
Once a year, my wife and I would invite two couples over on New Years Eve to have a Colonial meal. We used this oven to prepare the chicken. (the tin coating was long worn away, so, we lined the rear of the oven with aluminum foil to reflect the heat). My wife also made a beef stew in a Dutch Oven and also baked bread. All made in front of the fireplace. No electricity, only candles for lighting, and maybe some colonial music in the background. It was always a great hit with our guests.
Sorry to say, because of the rising cost of fuel oil, we had to resort to a wood stove in front of our fireplace. I miss our Colonial New Year Eve.