currently reads (it is wrapped in what looks like an HTML comment):
A sealed version of this set has been found to contain both solid stud and hollow stud minifig heads, indicating that the transition from solid to hollow stud occurred around this time."
Surely that should be "solid stud and blocked open stud minifig heads"
and "solid to blocked open stud" given that the hollow stud head was introduced
much later and the blocked open stud head appears in the sets inventory as an
alternate.