The answer to the question, what to do with old coins can vary greatly. A coin collector should take into consideration the type of coin that they collect and then work their way down the different eras in the history of the coin to see what can be made from them. For example, if you collect gold coins then your first step would be to look at gold coins in the gold standard era of coin collecting.
Antique collectors, on the other hand, do not usually want to collect coins from the gold standard era, since the value of these coins declined so dramatically after that time. Some collectors still collect coins from this time period, but they usually want to buy coins that are valuable in terms of their rarity. Other antique collectors like coins that are rare because they are not mass produced, so that their value is unique. Find out more about Coin Dealers UK at a site like https://www.gmcoins.co.uk/
A coin collector may be able to purchase old coins from dealers who specialize in trading in these types of coins. They would be able to tell you what to do with old coins, but you will have to do a little research on your own to determine what these dealers have to offer you. A better option is to check with some antique stores that specialize in dealing with coins. They will know what to do with old coins, and in some cases, they may even be able to give you some advice on where you should keep them or sell them to make some money.