The Heritage New Zealand-administered site near Maheno is one of the oldest original water-wheel flour mills in this country.
It also happened to be home to an infamous "speakeasy", Smokey Joe’s.
The unlicensed bar operated at the site from the 1940s to about 1971, Heritage New Zealand Pouhere Taonga property lead, Jacqui Allison said.
While Sunday is an opportunity to see the mill working, the return of items from the site’s speakeasy era means it is a grand opportunity to tap into Oamaru’s "unwritten history" when North Otago was officially "dry".
These include the original bar, a visitors’ book, and other colourful ephemera once on the walls of the bar.
Ms Allison said the "amazing pieces" had until recently been held by Warwick Clark.
Now having the items on site presented a real opportunity to broaden the visitor experience.
"It’s amazing as well from a capturing history perspective to have it come at a time when people are living in the community with memories of it."
She envisaged an oral history project where visitors including former punters will have "jogged memories" of the speakeasy’s heyday.
Back in the day, the bar was propped up by regulars officially toeing the line. Smokey Joe’s was a BYO-only private club.
However, the bar actually had a keg tap, "proof that alcohol was served here in useful quantities," Ms Allison said.
"It’s evidence of what everybody knew — that there were some sneaky dealings going on here."
Oamaru voted for prohibition in 1905. It finally came to an end in 1962, one of the longest local prohibition eras within New Zealand.
After World War 2, returned soldier Allan Clark, the father of Warwick, started Smokey Joe’s at the mill site, inspired by similar establishments he had encountered overseas.
"Allan became infamous for taking a less literal approach to the liquor laws that had kept the Ōamaru area dry for four decades."
In the day it was ostensibly a "music hall" but also served as a party and private function venue, clubrooms for various sporting organisations and an open-all-hours watering hole for those in the know.
The mill machinery will be running for the Clarks Mill Come Alive open day from 11am to 3pm.
It will include tours of the working mill, spanning the four levels of the main building, at 12pm, 1pm and 2pm.
The North Otago Vintage Machinery Club will also mount a display including a live chaff-cutting demonstration. There will be demonstrations of spinning and weaving, and home-made lamb burgers available to buy at the barbecue.
