During the past 50-60 years there has been a noticeable increase in the size of vessels visiting the upper harbour, with the result that new gross-tonnage (gt) records have often been established.
And today is the anniversary of two of those important milestones, both recorded by tankers.
On this day in 1956, the 12,146gt Kara became the first upper-harbour visitor more than 12,000gt.
Forty-five years later, the 31,255gt Probo Gull became the first more than 30,000gt to navigate the Victoria Channel.
Both represented two interesting classes of vessels.
Kara was completed in November 1955 by Rotterdamsche Droogdok Maats.
The 169.4m-long, 19,327dwt tanker belonged to a large class of 14.5-knot, steam turbine tankers built mainly for the Royal Dutch Shell group by Dutch and UK yards from 1953 onwards.
While those operating under the Dutch flag were given K names, their British flag counterparts had H names.
On top of this, eight others with San names built for Shell's affiliated Eagle Tanker Company later received H names when transferred to the parent company's fleet.
Nearly 50 of the class were built for the group.
Of those seen here, 16 flew the British flag, including Hastula, which made an earlier visit as San Fabian.
The last unit of the fleet to berth here, on December 8, 1974, was Koratia, one of the eight Dutch-flag visitors.
But this vessel differed from the rest of the large class as it was fitted with turbo-electric machinery.
Seven other tankers of the same design, built for various owners, also called at Dunedin.
Among them was the 12,166gt, 1958-built Irish Hawthorn, the only vessel registered in the Irish Republic to have called here.
It berthed on July 3, 1959, which also happened to be the anniversary of the first bulk petroleum shipment to Dunedin.
This arrived with Common Bros' "smallish" 5553gt steam tanker Malistan berthed on July 3, 1927.
Probo Gull, owned by the Torvald Klaveness interests of Oslo, had been in service since March, 1989.
The 182.8m-long, 47,980dwt vessel was one of six diesel-powered sister ships built at Pusan by the Korea Shipbuilding and Engineering Company.
The vessel was the first of an unusual type to call, as it was not a tanker in the true sense.
The "obo" part of its name denotes it was designed to fulfil different roles as an ore-bulk-oil carrier.
Kara's career came to an end when it was sold to South Korean shopbreakers at Inchon, who commenced demolition on March 6, 1977.
Probo Gull had two changes of name in 2004, firstly as Eships Gull, then Probo Bison.
It lasted until it was beached at Chittagong on July 2 last year, to be broken up after trading since 2008 as a Majuro-registered Gulf Ahmadi.
Compared with Kara, the overseas tankers that now call here have deadweight capacities ranging from 45,000 to 50,000 tonnes.
Currently the largest, at 31,534gt (49,982dwt), is the Chinese-owned CSC Amethys which berthed on April 1, 2010, and this year on January 5.
In port for the first time at the weekend was Hamburg-Sud's Bahia Blanca.
The ship now joins four other 41,483gt, 3630teu Bahia-class sister ships assigned to the company's Trident service which have been calling here regularly since they were introduced by Bahia on January 16 last year.
The third ship of the name in the fleet, Bahia Blanca was the second of the six Liberian flag sisters to be constructed by the Daewoo shipyard at Okpo, South Korea.
The newcomer was laid down on October 9, 2006, and delivered on February 12 the following year.
