A British Sixpence in 1805 has the purchasing power of about £1.40 GBP today.
A sixpence was worth 1/40 of a pound so it would be worth about $.04. (1/40 of $1.61)
Under pre-decimal currency in the UK, a shilling was worth twelve pence, and a sixpence worth six pence. The UK adopted decimal currency in 1971.
16.5 pence
Good luck if you have one, but the last British Sixpence was minted in 1967.
A sixpence is worth 0.25 GBP, so in Dutch that's 2.5 cent. There isn't really a word for a sixpence, as they never had that kind of coin. Also, the British sixpence coin was illiminated decades ago, so it no longer exists.
The exchange between a sixpence and American money varies widely on how well the market is doing. Currently, a sixpence is now only worth one U.S. penny.
A "Tanner" is a British colloquial term for a Sixpence. A "Halfcrown" is Two Shillings and Sixpence. There are five Sixpences (Tanners) in a Halfcrown.
2.5 pence
$1.50
The value of a 1949 Sixpence coin depends on its condition, rarity, and demand from collectors. In general, a 1949 Sixpence in average circulated condition may be worth a few dollars, while one in better condition or with unique characteristics could be worth more to collectors. It's recommended to have the coin evaluated by a professional coin dealer to determine its exact value.
A Sixpence was worth Sixpence in every year it was minted, which is why it was called Sixpence. This year being 2012, 98 years ago would have been 1914. Sixpence GBP in 1914 had the purchasing power of about £1.60 GBP today. NOTE - This historical conversion is the result of many calculations and considerations by a purpose designed program. The resulting answer should only be regarded as an approximation based on current exchange rates.
Sorry but no U.S. dollar coins exist dated 1805. Look at the coin again and post new question.