Boeing Model 40 with Liberty engine. Photo from L'Aéronautique March,1927
L'Aéronautique magazine
1927-03-01
<a rel="nofollow" class="external free" href="https://gallica.bnf.fr/ark:/12148/bpt6k65680209/f43.item">https://gallica.bnf.fr/ark:/12148/bpt6k65680209/f43.item</a>