I did a little sleuthing and have found out that this loom is a Structo brand loom. From comparing it to pictures, this one is maybe a model 600. This is what I found...It is all there except for one crank, I think!
Structo Artcraft 600 4-shaft loom with a maximum weaving width of 20". The loom came with a 15-dent reed. If the reed is slayed two threads per dent (for a sett of 30 ends per inch) the loom could accommodate 600 warp ends. It was made sometime around 1925 but before 1932 (when the next model was released).