Graphische Anstalt Otto Schloss; Otto Schloss KG, Berlin

Printers and publishers of cards from mid 1890's to after WW1, active in exports to the USA. The two logos are OS on a lithographic stone, and OSB in a shield. They were specialists in chromolithography, and it ironic that the first logo is used on the second example ad not the first.

There is an article on this firm at www.tpa-project.info/html/body_otto_schloss.html. (This suggests there may have been a third logo).