1791-1825: Pound Sterling/Rouble Exchange @ SPb
Although major calculations were always against the Silver Rouble rate, there were several variant moneys in Russia at this time, including:
a) Residual Silver Roubles (and minor Russian or foreign coinage in silver)
b) The Ruble of Exchange, or 'Rouble Effectif'
c) The Paper Ruble, or Assignat/Banco
d) Copper Coinage (Copecks)
e) Gold Ducat (Imperiales)
At the time of the establishment of the US currency until about 1798, there was Dollar-Rouble parity. Mexican (Spanish) piastres, basis for US Dollar Coin and nearly always at par, also circulated in Russia as money.
(Priced in Paper Roubles, the intrinsic value of other silver coinage is likewise informative.)
In 1800, 62 US ships visited Russia: American trade was increasing. Although the value of (coin) Silver Roubles was intrinsic and likely traded at an agio, when the Paper Rouble quickly depreciated (c.1801) US merchants began calculating on London, in Pence ; however, many cambists did not correct or update this data.
Alternately, the paper Rouble value of South American piastres (global trade Dollars) constitutes a Silver valuation (in Paper Roubles) and a simple proxy for USD$ forex 1800-1830.
c.1789/90: The Dollar/Rouble parity (1:1) assume because the Pound Sterling exchange?
c.1794: The 1789 Rouble-Dollar parity was quickly revised; however, this DATED/ERROR in forex persists in many currency tables for the next two decades
c. 1795: the Silver Rouble at nearly 400 grains troy (25.894 g) Fine Ag and worth ~USD$ 0.87 - 0.90 (1790-97)
c.1795: 1 ozt Fine Silver (English Coin) = 1.59 руб
1797:1799: Paper Rouble, ~24 d (£0.1)
1800 Price Index (much more data at this source)
c.1800: 1 Rouble (?) = USD$ 0.66
1801: 1 Rouble = £0.125
June, 1805: Silver agio 30%