Bolex H16 User
For Practical Bolex H16 Filming
Bowl Head Adaptor
Bolex Product Code PIBOL (Head 3)
Bolex
introduced a bowl head adapter which could provide perfect leveling of
the tripod when used on uneven ground.
You can spot when a second type of tripod has this feature by looking under the head and parallel to the legs should be a round handle protruding 5 inches from the head.
When unscrewed this loosens the bowl head which can be moved in all directions so as to level the tripod when on uneven ground using the built in spirit level.
The spirit level is included on all heads regardless
if they had the 
bowl
head adapter on them when they were shipped from the factory.