No. 3 Kodak Junior (1889)
After the introduction of the original Kodak in 1888 new and bigger sized models appeared in 1889 and 1890. Their picture size was designated with numbers:
No. 1 for the original round photo of 2.5 inch (6,3 cm) diameter
No. 2 for a round photo of 3.5 inch (9 cm)
No. 3 for a 3.25 x 4.25 inch (8,3 x 10,8 cm) picture
No. 4 for a 4 x 5 inch (10 x 12,5 cm) photo.
The camera in this video is a No. 3 Kodak Junior.
The difference between a No. 3 Kodak and the No. 3 Kodak Junior is the detachable rollfilm back, that can be replaced with a plate back. In the video both backs can be seen. The plate back has a ground glass and two doors, one for the plate holder (open in the video) and one at the back to be able to see the ground glass.
Why these cameras were offered with a plate back is explained in the 1892 catalog: "...there is now really no reason why anyone should use glass plates. As we do not expect, however, to convert the whole world in a day, we supply many styles of Kodaks with glass plate attachments for those who prefer to stick to old methods."
The No. 3 Kodak Junior was introduced in December 1889 and discontinued in 1897. Its price was $ 40, so it was not really aimed at people with a small purse.
Page from the Kodak 1890 catalog.