Looking at past editions of Top eBay Chess Items by Price, I find autographed items featured nearly every year. Last year we had Capablanca to His Son (June 2015), and the year before Alekhine Dozes at the Board (January 2014).
The item below was titled 'RAUL CAPABLANCA AKIBA RUBINSTEIN SIGNED AUTOGRAPH World Chess Championship' and sold for US $899.99 Buy-It-Now. The mention of 'World Chess Championship' and the subtitle 'OTHER FAMOUS CHESS PLAYERS APPEAR ON THE DOCUMENT' indicate that the seller wasn't a specialist in chess history.
The description only repeated the auction title and added short bios for 'Akiba Kiwelowicz Rubinstein' and 'José Raúl Capablanca y Graupera', both probably copied from Wikipedia. The item shows 13 autographs on the left plus a legend in the upper right. The lower right mentions Bad Kissingen 1928.
The numbered signatures -- from Kostich [who did not play in the event], Nimzowitsch, Tarrasch, Euwe, Marshall; Yates, Reti, Mieses, Tartakower, Spielmann, Capablanca, Bogoljubov, and Rubinstein -- account for all 12 players. The numbers on the left all use the same ink as the corresponding signature, indicating that they were not added afterwards.
A few years ago I had another post about 1928 Bad Kissingen (July 2014), where I featured an eBay photo. The photo in that post and the signatures on this current post echo a postcard shown on 4465. Bad Kissingen, 1928 (chesshistory.com; July 2006).