J. JOST.
image by Jorge Candeias, 2 May 2004
Massary 1930 names E. Jost, probably an initial error.
Jorge Candeias’s J224 rendition is blue with two white triangles facing one another. Jarig Bakker identifies J. Jost from Wolter’s 1968 book, though Rosanoski notes that its J225 version is not quite the same. The book indicates very dark blue, almost black.
The Bremer Schiffahrtskontor Brink & Wölffel flag is almost the same, but its white hourglass reaches the upper and lower flag edges.
The additional variants remain documented in the respective flag books and charts, without a separate verbal design description in this source.