Stern said Rheinmetall's plan, first exposed by a journalistic consortium last March, foresaw a joint venture in Turkey to produce 1,000 tanks worth 7 billion euros ($8.3 billion) in total.
Intended was a Turkish-designed tank, the Altay, equipped with German technology, which could be fitted with a bulldozer-like shovel, "practical" for dealing with street protests.
Stern fronted its article in this week's edition with what it said was previously secret photograph of the gathering at Istanbul's Yildiz Palace in November 2015. One of the authors of the story, Hans-Martin Tillack, tweeted the photo with the caption "Tomorrow in #Stern: How #Rheinmetall got President Erdogan's "political blessing" for a tank factory."
Visible were Erdogan, three Rheinmetall managers, and business partners from Malaysia and Turkey, including the leading Turkish vehicles firm BMC.
The photograph's emergence coincides with persistent debate in Germany about Turkey-EU links and arms exports.
Chronologically, that 2015 meeting came eight months prior to last year's coup attempt that has since resulted in a massive crackdown by Erdogan's administration.
Stern said it had also obtained a 16-page Rheinmetall presentation that "sketched how the German concern could upgrade Erdogan's army."
That document indicated that in 2015 the Turkish president had already given the intended joint venture his "personal blessing," Stern said.
"The partners from Turkey and Malaysia needed Rheinmetall not so much because of the technology, but because of its [Rheinmetall's] good connections to Erdogan," Stern claimed.
One of the key figures was a Malaysian tycoon, who, according to Stern, became a stakeholder in the Turkish joint venture in the second half of 2016.
The intended joint venture's key player was the Izmir-based BMC, which largely makes Turkish trucks and buses. Rheinmetall had a 40-percent stake in the once intended venture, according to the German news agency DPA.
"Until now, [German] armaments firms need a permit from the government, if they want to export weapons or blueprints for weapons – not, however, if they send experts into countries such as Turkey to provide 'technical support'," Stern said, in a reference to German debate about the ethics of arms exports.
In May, shareholders at Rheinmetall's general meeting in Berlin elected former German defense minister Franz Josef Jung of Merkel's conservative Christian Democrats (CDU) to the concern's supervisory board.
Venture plan 'inactive'
The magazine said Chancellor Angela Merkel's coalition government had to date not criticized the envisaged project and it quoted a Rheinmetall spokesman as saying that the joint venture was "at the moment nonactive."
Last March, the Düsseldorf-based Rheinmetall said it still planned to tender for contracts in Turkey.
"Turkey remains as before an important trading partner for Germany, a fully integrated NATO partner and as before an EU accession candidate," said Rheinmetall, adding that whether venture with BMC proceeded hinged on clearance or not from Germany's government.
A concern spokesman said Rheinmetall only planned to modernize German Leopard II tanks already in NATO-partner Turkey. "A tank factory of Rheinmetall in Turkey doesn't exist," the spokesman asserted.
In March, opposition German Left party parliamentarian Sevim Dagdelen told Stern that Rheinmetall's intended partnership was a "monstrous affair."
Opposition Greens party spokesman Omid Nouripour described the matter as "absolute madness."
In June, at Germany's Protestant church convention in Berlin, activists of the citizens group Campact displayed banners with the slogan "No tanks for Erdogan" during an speech by German Foreign Minister Sigmar Gabriel.
Gabriel at the time called for disarmament world-wide and criticized President Donald Trump for US plans to massively boost arms supplies to Saudi Arabia.
ipj/kms (dpa, epd, Reuters)