1848-1852 American(?) Apollo lyre at the Metropolitan Museum of Art, New York - It's interesting to see, looking back over the years, just how much experimentation went on in creating the musical instruments we know today. For instance, this is the only known "Apollo lyre" in existence - according to the curators, "The upward-pointing handles produce pressure and suction to sound a diatonic scale, as in an accordion or harmonica."
One of the oldest preserved harps in the world, is from Scotland. This harp, dated 16th century, similar in design to the Brian Boru Harp of Ireland, is ornamented with gems and has a geometric relief carving on its column. It's in the National Museum in Edinburgh.
1770 English Cittern at the Museum of Fine Arts, Boston - Citterns were instruments dating back to the Renaissance. However, in England, they continued to be used for casual music-making well into the 18th century; for instance, one might be kept in the waiting room at a barber shop so clients could amuse themselves as they waited. In that way, they were similar to acoustic guitars today, where many people could play one just for fun.