Although the value of any coin is heavily dependant on the date it was 'minted' or created, the L.500 coin is not thought to be of any particularly significant value.
If in poor condition, its value could be as little as 20 US cents, but if it is in very good condition it could be worth up to $3.
The Italian Lira
The lira (or lire if plural) was the Italian currency from 1861 until 2002 when the euro took over as the legal tender of Italy. The word lira comes from the Latin word libra, and was based on the value of a pound (in weight) of highly pure silver.
Because of this, the lira is directly associated with the British pound sterling which is so-called for much the same reason.
In some countries, like Malta and Cyprus for example, the words pound and lira were interchangeable.
Lira banknotes were, until recently, exchangeable for Euros in any branch of the Bank of Italy, but the deadline for changing all lire passed on February 29th, 2012. At the time of it being phased out, the exchange rate was 1,936.27 lire to the euro.
The currency of the Vatican State
Up until the advent of the euro, the Vatican City State and San Marino had their own lire, which was their official currency. It equaled the Italian lire in all ways and could be used as legal tender throughout Italy, but was specific to each of these two places and was minted in Rome. Nowadays, both the Vatican City State and San Marino use the euro as their currency, but again, they have their own sets of coins.
Italian Euros
All Italian Euros have a unique design on each denomination of the coin but the common theme is that of a famous Italian work of art. They also have the twelve stars of the EU on them and the overlapping letters, RI, which stand for Repubblica Italiana - and another letter R, for Rome.
To put it frankly, the value of the L.500 depends when the coin was made or 'minted' as the terminology goes.
If it's a 1961 coin, commemorating the 100th Anniversary of Italian unification, then you're looking at a melt value of around $6 (as they're roughly 80 per cent silver). Obviously the significance of the coin adds value so you might be looking at above $20 if you can find the right buyer.
If it's a 1982 bimetallic coin (bronze and steel) then $2. If it's a 1982 coin with Christopher Columbus on the reverse then you could be looking at up to $30.
Another 500 Lire coin from 1982 commemorates the 100th anniversary of the death of Garibaldi as usually goes for around $25.
If it's a bimetallic coin from 1984 then it's valued at around $10.
And it's the same kind of price for a bimetallic one from 1987, roughly $10.
It is also important to note that coins that have been in circulation are worth significantly less than those in mint conditions: Up to 50% less at times.
As with all coins, if you're not desperate to sell, keep hold of them as their value is highly unlikely to depreciate and they are more much likely to increase in worth.