Re: Gold cluster medals
What Jack said was that "oak leaf clusters" are not awards in themselves but are a convenient way of showing that an honoree has won a certain medal more than once.
If we are all talking about the same thing then your father won a standard military medal of some kind and was later awarded the same medal at least two more times. To know what the "oak leaf clusters" mean you have to know what the original award was.
Medals are not normally worn on military uniforms. Instead, a small ribbon is worn and the oak leaves are pinned to them. If you have an oak leaf mounted on a ribbon the ribbon identifies the medal your father was awarded.
There are probably web sites that illustrate all known military medals and their characteristic ribbons.
If you have acopy of your father's DD 214 it should name all his awards.