1807 entire to Riga bearing straight line ST.PETERSBOURG handstamp, backside manuscript '16K'. On November 14 1783, the postal rates in the Russian Empire were made uniform by decree. The rates were valid until 1830. Letters weighing <a href="https://en.wikipedia.org/wiki/Obsolete_Russian_units_of_measurement" class="extiw" title="w:Obsolete Russian units of measurement">1 lot</a>, (12.7974g / 0.451 oz), were charged per 100 <a href="https://en.wikipedia.org/wiki/Verst" class="extiw" title="w:Verst">versts</a> distance (the verst was 1.0668 km / 0.6629 mile): 
<ul><li>Up to 100 versts 6 kopeks</li>
<li>Between 100 and 1500 versts 2 kopeks per 100 versts</li>
<li>Between 1500 and 3100 versts 1 kopek per 100 versts</li>
<li>&gt; 3100 versts 50 kopeks.</li></ul><p>This letter was assessed at 16 kopeks, which equals 6+5x2=600 versts or 640km / 398 miles.
</p>
<ul><li>Postmark 'ST. PETERSBOURG' Dobin 00.00 type 01B used from 1775-1809, used as dispatch and transit mark for foreign mail, rarity 7<sup id="cite_ref-1" class="reference"><a href="#cite_note-1">[1]</a></sup>.</li></ul>
Russia Post
1807
Self-scanned