I believe the 90 degree stop first appeared about 1985-86. This was about the same time as the combo tool was introduced.
The first part is correct (half stop on 84mm combo tool appears circa 1985) . The second part not quite. The 91mm combo tool appears around 1985/6, but the 84mm version dates back officially to 1980 and unofficially to the late 1970s according to some SOSAK members who remember buying them in the late 1970s.
There are three different versions of the 84mm combo tool - the original version with the rounded over tip does NOT have the half stop. The second and third versions do. The second version appears c. 1985.