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Vaestra Sallerup church, Lund diocese
Vastra Sallerups Kyrka, Sweden
Two church paintings from Skane (Scania) - at the time when it was still Danish and not Swedish - shows that boxed Kastenbrust's were used up here even into the 1440's.
Vester Sallerup Kirke/Vastra Sallerups Kyrka.
Dating is unclear because the inscription "Klaos" could refer either to the knight or the kid.
A) If the inscription refers to the kid then the church paintings has to be dated already around 1415, when Klaus Nielsen (Sparre af Ellinge) was 6 years and the knight in the boxed Kastenbrust is his dad Niels Svendsen (Sparre af Ellinge), who was knighted in 1411.
Such an early date for a Kastenbrust in Denmark sounds currently unlikely, but not entirely impossible.
B) If the inscription refers to the knight, then we have to date it around ~1445.
Klaus Nielsen (Sparre af Ellinge) is knighted in 1441 and then the kid in the painting is his son Niels Klausen (Sparre of Ellinge) - (he will be knighted in 1497).
I find interpretation B) to be the far most likely given our current evidence, though it goes against the common scholarly view, which probably have focused in the inscription being over the head of the kid. But if you have to name one person, why not the person who achieved something (like being knighted), instead of a kid who might not even make it to adulthood given the high child mortality in former times.
Furthermore a 1440's dating for boxed Kastenbrust's in Denmark does seem likely, if we hypothesize that Dwnmark is generally some decades late in fashion compared to the Rhine area.

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Pernille Thott i vidbrattad hatt. Sonen Claus mellan henne och hennes man Niels Sparre i riddardrakt. Hans far Svend Jonsen gar forst och ger en gava (ciborium) at Balthasar, den yngste av de tre vise mannen

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Some of the paintings depict the coat of arms of the Sparre family of Ellinge Manor.
The arms on the southern side represent the male members, whereas the arms on the northern side represent the female members.

Skane (Scania)
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Diocese of Lund
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(Link) Klaus Nielsen (Sparre av Ellinge) (1409-1451)

Датировка 1415? кажется более вероятной, исходя из похожих изображений:
A0034, 1420? - длинные рукава, короткий подол, пояс, кастенбруст с ребрами, кольчужный воротник
A0007, 1410? - длинные рукава, короткий подол, пояс
A0041, 1410? - длинные рукава, короткий подол, пояс
P0007, 1415 - длинные рукава, пояс, кастенбруст с ребрами
в более позднюю дату (~1445) более обычными были длинные подолы, часто покрытые кольчужным фартуком
датировку 1415? поддерживает и тот факт, что на изображении присутствует жена персонажа, мать Клауса, умершая в 1418 году
а изображенный малолетний персонаж с надписью "Klaus" вполне соответствует возрасту (в 1415 ему было около 6 лет) сына нашего персонажа