An Antiquity study counts 500 La Tène iron bars in a tonne of metal dredged from the Danube

The 500-sword figure is a conversion of mass. Trebsche puts an average sword at 1.5 to 2 kg ^[10]. A metric ton divided by 2 kg gives exactly 500; divided by 1.5 kg it gives about 667 ^[23]. The sword count therefore sits at the heavy end of the range Trebsche himself supplies, before any allowance for metal lost in forging. He addressed that directly. "Even if we take material losses during manufacture into account, the iron from Deinham would have been sufficient to equip a large group of warriors with weapons," Trebsche said ^[12]. His other conversion, up to 8,000 nails ^[11], implies 125 g of iron per nail ^[24].

The bar count is a floor. The team identified 193 complete bars and 307 partial ones ^[3], so 39% of the assemblage survived whole ^[27]. At the reported mean of about 2 kg, the complete bars come to roughly 386 kg, leaving something over 600 kg spread across the 307 partial bars, close to 2 kg each ^[25]. Either most of those partials are near-whole bars, or the one-tonne total is rounded. Both published accounts give the average complete bar as 28.5 cm long and about 2 kg ^[4]. A claim about standardized production would rest on the spread around that mean, and neither account reports it.

Where the metal came from is an inference from form and geography. Bars of the same double-pointed shape are known from Manching in Bavaria, about 200 km away, and the authors write that it is plausible the Deinham bars were forged there ^[15]. Manching lies near a large iron mining area, and several Iron Age production sites have been found close to Bavarian oppida ^[22]. Nobody knows where the iron was headed ^[28]. Trebsche and Berranger are now analyzing trace elements in the bars, which may narrow the source ^[16].

The value comparison in the paper runs through gold. A hoard at Manching holds 443 coins totalling 3.7 kg of gold, and the authors suggest that sum could plausibly have been worth about a ton of iron ^[17]. That is roughly 270 kg of iron per kilogram of gold ^[26].

The paper's title ends in a question mark: "A sunken ship cargo of 500 bipyramidal bars?" ^[21]. The bars came out in an excavator's gravel, which destroyed the find context and with it the chance to establish how the iron entered the river ^[13]. "The possibility of ritual deposition cannot be excluded," the authors wrote, though "most studies on river finds have concluded that iron bars are losses incurred during transport" ^[14]. Trebsche said: "It is incredible that such a large quantity of iron was transported at once and was available in a single exchange transaction in the Late Iron Age." ^[18] Confirming a single transaction would have taken the context the excavator destroyed. Radiocarbon puts the metal in the La Tene period ^[8], and the study text narrows it to the third and second centuries BC ^[7]. What that dates is a population of bars, not one sinking.