The 645 series was introduced in 1975 with the 1000s coming in 1976. I believe they continued to make the 1000s until 1990.
The camera is an SLR with an image format of 6cm x 4.5cm. You get 15 frames on a 120 roll and 30 frames on a 220 roll. The film is put into inserts which then go into the camera. 120 and 220 films use different inserts presumably because of the need for different pressure plates due to the lack of paper in 220 film. Later models used magazines which could be swapped mid roll.
Here are a few test shots from the first roll.