Image illustrates American Chemical Society logo including chemical instruments being an <a href="https://en.wikipedia.org/wiki/Alembic" class="extiw" title="wikipedia:Alembic">alembic</a>, <a href="https://en.wikipedia.org/wiki/Hydrometer" class="extiw" title="wikipedia:Hydrometer">hydrometer</a>, and <a href="https://en.wikipedia.org/wiki/Pressure_measurement" class="extiw" title="wikipedia:Pressure measurement">ionization indicator</a>.
<a href="https://en.wikipedia.org/wiki/Bureau_of_Engraving_and_Printing" class="extiw" title="wikipedia:Bureau of Engraving and Printing">Bureau of Engraving and Printing</a>; Imaging by <a href="//commons.wikimedia.org/w/index.php?title=User:Jphill19&amp;action=edit&amp;redlink=1" class="new" title="User:Jphill19 (page does not exist)"><i>jphill19</i></a>
1951-09-04
U.S. Post Office