The result cuts in one direction only. A blade that still shows the intersecting bands of kamacite and taenite comes with a temperature ceiling attached, because that structure grew over millions of years of slow cooling inside an asteroid and cannot re-form in a forge once heat has taken it out [12][13]. An unpatterned blade leaves its iron's origin undetermined [11]. The pattern's presence is a measurement; its absence is a gap in the record.
What survives the fire is chemistry. The attribution of Tutankhamun's dagger rested on a nickel and cobalt assay, not on a polished surface [7], and that is the screen Laura Noel Garcia points at for everything else: high nickel and cobalt with no visible bands is a candidate rather than a closed case [10]. The bands became the convenient marker because they are unmistakable once the metal is cut and polished [12]; other lines of evidence exist too.
Earlier reconstructions put the dagger's forging at 800 to 950C [8]. Set that against the band in which the team's samples lost the pattern completely, and the whole of the proposed window sits at or above the temperature where the structure went [2]. The two published claims can hold for the same blade only if what is visible on it is not really a Widmanstatten pattern; the study's own condition is "if the structure observed on its blade is indeed similar", and its answer is that preserving such a structure would require considerably cooler work [8][9]. The dagger itself was never re-forged. The experiment sets limits on how the artifact can be read, rather than measuring the artifact directly.
The thing this doesn't tell you is where, between 650 and 800C, the bands actually go. The tested windows were 600 to 650, 800 to 850, and 1100 to 1150C [5], which leaves the 150 degrees between "begins to change" and "gone completely" unsampled [1]; across the whole span tried, the three windows cover about 150 of 550 degrees, roughly a quarter of the interval [3]. The material was a single octahedrite worked by one blacksmith [4], and the hammering imitated traditional forging only as far as a controlled run allows, which is the study's own qualifier [5]. A working smith's fire has gradients and dwell times that a bracketed heat does not reproduce.
The negative finding still stands, and that is the part that transfers. A destroyed microstructure stays destroyed at any of these temperatures, so the direction of the error in the existing literature is known even if the threshold is not: objects have been read as terrestrial for lacking a feature that ordinary hot work removes. Iron artefacts from the Late Bronze Age and Early Iron Age that were filed as earthly because they looked plain are now untested cases [10], and testing them means an assay, not an etch.
