The following scans were made from original photographs that were sold in Germany 1929 when real Sioux Indians were visiting Germany with the Circus Sarrasani and my grandfather saw them in Loerrach.
I tried to find more links in the net but these seem to be rather rare and I intend to add the pictures to Wiki entries about Sarrasani (though I'm not sure whether I could get into copyright troubles with them).
Preview:
My grandfather was a big fan of the USA and native Americans - like most Germans, thanks to Karl May and his awesome and completely invented Wild West stories. When he was prisoner of war in WWII and shipped around half the world and back, he'd totally have stayed in the US but my grandmother didn't want to emigrate (what a pity :)
One of the Indians signed one of the cards; the other was obviously written by my grandfather - ah, he was such a Wild West fan, I grew up on Wild West posters and art and Doc Holiday and Wyatt Earp penny dreadfuls (I read 800 of them in 1980 *G* - addiction, your name is Syredronning...)
I'll send these postcards to
eldritchhobbit who does real research and documentaries and writes books about Native Americans, especially Sioux, and I hope she'll make good use of them. I thought about keeping the one my grandfather signed (maybe maybe). OTOH, these cards almost got thrown away several times just in my lifetime, so it's a good thought they'd go "home" to people who do something with them instead of keeping them in a drawer.
This link here goes to a Karl-May-Event in 1928, but it's German with no great pictures:
http://karlmay.agerth.de/wiki/index.php/Indianerehrung_1928