Welcome to the forum Thoran98, I would say it is a MK4 helmet rivets on the MK4 helmets were lower down the side
than the MK3 helmets which were higher up.
These helmets were produced by three companies.
Briggs Motor Bodies Ltd ( BMB ) of Dagenham
Fisher & Ludlow Ltd ( F&L ) of Castle Bromwich
Ruby Owen Co Ltd ( RO & CO ) of Leeds
Looks like the rivets have been replaced by nut and bolts.
hope this helps.