You might have owned a few shares in 1973 but you would definitely not be trading them , the NZSE wasn't up and running in full till 1983 after the amalgamation of many regional exchanges . Brokerages were not licenced till the mid 80's .
" On 24 June 1991, NZSE implemented a computerised trading system, and abolished the open outcry market. This computerised system was replaced with the FASTER trading system in September 1999."
Facts numbskol ,
NZX began life as a number of regional stock exchanges during the gold rush of the 1870s.