Some of the very much older banknotes will have the date of issue prominently displayed on them.
Alternatively, the first step is to identify the Chief Cashier which will place the note into a range of years for which that individual was the Chief Cashier of the Bank of England.
Second step is to identify the leading characters of the serial number.
With this information, you can consult a banknote catalogue and come fairly close to the year of issue.
The Bank of England Ten Shilling note was last issued on 13-Oct-1969 and ceased to be legal tender on 22-Nov-1970. It was replaced by the 50 New Pence coin which was first issued in 1969.
I have no way of knowing whether or not it was circulated, but the serial number of the last Bank of England Ten Shilling note commenced with D38N and possibly ended with 999999.
Without additional context, the value of a Bank of England Ten shilling note with serial number 18Y 015906 would depend on factors such as its condition, rarity, and demand among collectors. I recommend consulting with a currency appraiser or a numismatic expert for a precise valuation.
Other than for the old white banknotes, the Bank of England does not usually put the date on its banknotes. To figure out the approximate year of printing, you need to find who the Chief Cashier was whose signature appears on the note, and the serial number. A combination of these things should get you an approximate year.
A new Bank of England Fifty Pound note featuring Matthew Boulton and James Watt was issued into circulation on the 2nd of November, 2011. The older style Bank of England Fifty Pound note featuring Sir John Houblon will be progressively withdrawn from circulation at a date to be advised after a public announcement from the Bank of England.
A Bank of England Ten Shilling note (Series C - red/brown)(Chief Cashier L.K. O'Brien - serial H47), circulated but still in good condition, might fetch anything from £2 to £8 GBP. A reputable coin dealer will be able to give a more accurate valuation.
A Bank of England Ten Shilling note (Series C - red/brown)(Chief Cashier L.K. O'Brien - serial C02), circulated but still in good condition, might fetch anything from £2 to £8 GBP. A reputable coin dealer will be able to give a more accurate valuation.
Please check the serial number and provide the name of the Chief Cashier if possible.
A Bank of England Ten Shilling note (Series C - red/brown)(Chief Cashier L.K. O'Brien - serial T41), circulated but still in good condition, might fetch anything from £2 to £8 GBP. A reputable coin dealer will be able to give a more accurate valuation.
A Bank of England Ten Shilling note (Series C - red/brown)(Chief Cashier J.S. Fforde - serial C89N), uncirculated and in absolute mint condition could fetch anything up to £10 GBP. If it has been circulated, not much. A reputable coin dealer will be able to give a more accurate valuation.
A Bank of England Ten Shilling note (Series C - red/brown)(Chief Cashier J.S. Fforde - serial C39N), uncirculated and in absolute mint condition could fetch anything up to £10 GBP. If it has been circulated but still in good condition, not much. A reputable coin dealer will be able to give a more accurate valuation.
It is worth 5 pence if you mean the English shilling