Raab-Katzenstein RK 25 "Ruhrland" racing aircraft for the <a href="https://en.wikipedia.org/wiki/Challenge_International_de_Tourisme_1929" class="extiw" title="en:Challenge International de Tourisme 1929">Challenge International de Tourisme 1929</a>
Unknown author<span style="display: none;">Unknown author</span>
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