Item consists of a wooden box used for black and white film developing, containing a stainless steel round metal film tank and reel for 120mm film, 2 handles for film winding that fit through holes in the box, 1 film spool, and a metal instrument. A metal spool holder is mounted to the inside of the box. To use the developing tank, the film backing paper is attached to a spindle in the wooden developing tank, along with a light-tight cover, all of which are wound onto the spindle. The spindle is then transferred to the metal developing tank to be processed.

Source: Early Photography (2019). Roll-film developing tanks. Retrieved from: http://www.earlyphotography.co.uk/site/entry_D70-X.html