If the coin remains undamaged by the jewellery making process -
A British 1893 sterling silver Crown (Five Shillings)(Victoria)(Regnal date LVI), uncirculated and in absolute mint condition could fetch up to £350 GBP. If it has been circulated but still in good condition, it might fetch up to £15 to £160 GBP.
A British 1893 sterling silver Crown (Five Shillings)(Victoria)(Regnal date LVII), uncirculated and in absolute mint condition could fetch up to £600 GBP. If it has been circulated but still in good condition, it might fetch up to £25 to £300 GBP.
The values quoted are the best possible for the best specimens in their grades, but may be significantly lower due to varying demand for the coin and the prevailing economic climate. A reputable coin dealer will be able to give a more accurate valuation based on inspection of the coin.
Modified coins have no collector value. Any value the pendant may have would be as a piece of jewellery. The coin itself might get up to £2 GBP if it was in mint condition and had not been silver plated.
There was no 1946 British Crown minted.
The value of a 1939 George VI British silver half crown can vary depending on its condition and wear, but ranges between $3 and $20.
No web site can give you the value of any object, sight-unseen. Take your pendant to a jeweler, or to a pawn shop and ask for a valuation.
There was no 1908 British Crown (Five Shilling) minted.
There was no 1956 British Crown (Five Shillings) minted.
There was no 1923 British Crown (Five Shillings) minted.
There was no British Crown minted from 1938 to 1950 inclusive.
There was no British 1907 Crown (Five Shillings) minted.
There was no British Crown minted from 1903 to 1926 inclusive.
There was no British Crown minted from 1848 to 1886 inclusive.
There was no 1963 British Crown (Five Shillings) minted.