So they could be makers marks, draw weight marks using some unknown standard of draw weights, or what about inspectors marks like how early firearms were inspected and marked?
Or a combination of the last two perhaps the number of marks indicating weight and the layout the location of the government inspector? I'm sure they tested each bow somehow when they were delivered by the makers? I can't imagine them paying for them without testing or inspecting them.
Just a thought but has there been any correlation with similar marks on any surviving munition armor (something the government would have provided to lower ranking soldiers as opposed to private purchase), firearms, or any other contemporary military equipment? I think by later Tudor times some of it was starting to be provided by the government as private livery had gone out under Henry VIII's father. This would point to a type of inspectors mark