When Glencore announced it was curtailing 500,000 tonnes of capacity at its zinc mines in October 2015, the price of three-month zinc on the London Metal Exchange was $1,700 per tonne.
The price is now $3,175 per tonne, hovering within striking distance of last month's 10-year high of $3,326.
Glencore can't take full credit for the bull surge of the last two years but its curtailments acted as a powerful accelerator to a structural shift towards supply deficit.
So what happens next, now the company has just announced the first restart at the Lady Loretta mine in Australia?
The market seems unfazed. Indeed, LME zinc rallied on the news, the bear sting masked by a headline decline in forecast production next year.
It's probably right to be sanguine. Glencore has delivered exactly what it had previously signalled. The restarts will be both partial and gradual and will take a long time to feed through into the refined metal part of the supply chain.
And refined zinc still looks super tight, although there are warning signs for bulls, not least Glencore's own purchase of a stake in a mothballed plant in the United States.
TESTING THE MARKET
Exactly one year ago, Glencore executives were fielding questions as to when the company would return its 500,000 tonnes of capacity to the market.
Any reactivation, according to finance chief Steven Kalmin, might be staged over a period of time as a way of testing the market.
And each mine, added Chief Executive Ivan Glasenberg, could take at least nine to 15 months to reactivate, with the option of bringing them back one by one rather than all together.
Which is precisely what Glencore is now doing. Lady Loretta, part of the Mount Isa complex in Queensland, will start ramping up in the first half of next year and will hit full 160,000-tonne per year capacity only in 2019.
The other two thirds of the capacity will remain mothballed until further notice.
Which is one reason why Glencore is forecasting headline group zinc production to decline to 1.090 million tonnes in 2018 from 1.105 million this year.
The other, less obvious reason is the sale, completed at the end of August, of controlling stakes in two African mines to Canada's Trevali Mining.
Between them Perkoa in Burkina Faso and Rosh Pinah in Namibia will produce 125,000 tonnes of contained zinc this year, according to the mid-point of Trevali guidance.
Both dropped out of Glencore's production figures effective September, although after the transaction it is now Trevali's largest shareholder with 25.54 percent of outstanding shares.
Lady Loretta's production will start feeding into a tight zinc concentrates market only around the middle of next year.
Any impact on the refined zinc market is months away and the size of the restart should be seen in the context of the International Lead and Zinc Study Group's most recent assessment of a 401,000-tonne metal deficit over the first 10 months of this year.
That deficit is mirrored in falling exchange stocks.
LME zinc inventory is at a nine-year low of 195,225 tonnes. Available metal, not including that marked for physical load-out, is 164,350 tonnes.
Since the middle of October, arrivals have been limited to a single warranting of 2,750 tonnes at New Orleans on Nov. 14 despite a persistent premium on cash metal.
In Shanghai, the zinc contract has also been trading in backwardation but with equally little impact on stocks. At 65,772 tonnes as of Friday, these are down by 87,000 tonnes on the start of the year and back at levels last seen in early 2009.
It's also noticeable that China's net imports of refined zinc have stepped up a gear in recent months with the January-October tally now up 22 percent year-on-year at 438,500 tonnes.
Everything, in other words, seems to be painting a picture of supply chain stress.
Well, just about everything.
The LME zinc backwardation has been steadily easing over the last month or so and it's disappeared altogether this week. The benchmark cash-to-three-months period CMZN0-3 was valued at a small $0.50-per-tonne contango at Wednesday's close. The same spread was valued at $91 backwardation at one stage in October.
LME spreads can be an opaque part of the market at the best of times and right now extra complication comes from funds rolling index positions, a dominant long position holder navigating the exchange's lending guidance and the usual end-of-year book-keeping.
But the disappearance of the cash premium still looks anomalous in light of the continued erosion of LME inventory.
The spreads collapse could be signalling more metal is on its way. If not, contango isn't going to last very long.
FIRING BACK UP IN NORTH AMERICA
In terms of what's happening in the refined metal part of the zinc market, this week's restart news has overshadowed two other significant developments, both also connected with Glencore.
Noranda Income Fund announced on Nov. 27 that the long-running strike at its CEZ refinery in Canada had ended.
The Quebec plant, which acts as a tolling partner for Glencore, saw production fall by 70,000 tonnes over the January-September period, a significant drain on North American availability.
Glencore's other bit of zinc news largely slipped under the collective radar.
On Dec. 8 it bought a 10 percent stake in American Zinc Recycling Corp (AZR), the new entity that has emerged from Horsehead Holding's Chapter 11 bankruptcy proceedings.
AZR is looking to restart the 150,000-tonnes per year Mooresboro zinc refinery in North Carolina.
Mooresboro uses unusual technology, processing zinc-rich waste from steel mills and other secondary sources to produce refined ingot. The plant was plagued by technical problems in the two years it operated prior to being idled at the start of 2016.
Under the terms of the deal with AZR, Glencore will provide "engineering and project management services directed at accelerating the restart of the Mooresboro Refinery".
Glencore's continued investment appetite in the zinc sector is a strong signal it doesn't believe the bull party is over yet.
And it's certainly not going to be the one to snuff it out by bringing back too much mine capacity. It's clear there's not going to be any "big bang" restart moment, but rather a series of little "bangs" to test the market.
Shorter-term bangs in terms of refined metal availability will come from the end of the CEZ strike and, potentially, a restart of Mooresboro.
Right now, though, the biggest red flag for zinc bulls is what's going on with those LME spreads. (Editing by Dale Hudson)