Here are my contributions for today's theme at See It On A Postcard.
The stamp on the left was issued on 13 October 2011 under the theme, At Home in Germany: German Inventions. Among these 3 objects, the MP3 player qualifies for the theme. MP3 is an acronym for an audio coding format that was developed and enhanced mostly in the 20th century.
On the right , we have the Schmidt camera or telescope. It was invented in 1930 by the German-Estonian optician Bernhard Schmidt. The stamp was issued by Latvia in 2 April 2009.