[System.AttributeUsage(System.AttributeTargets.Class |
                       System.AttributeTargets.Struct |
                       System.AttributeTargets.Field)
]
public class PGFSerializeable : System.Attribute
{
}

public class TestMBObject : MonoBehaviour
{
    [PGFSerializeable]
    public int m_testInt;

}

        FieldInfo[] fieldInfo = typeof(TestMBObject).GetFields();
        for (int i = 0; i < fieldInfo.Length; i++)
        {
            Debug.Log("-----\nPGFSerializable fields for " + fieldInfo[i].Name + ":");
            object[] customAttributes = fieldInfo[i].GetCustomAttributes(false);
            for (int j = 0; j < customAttributes.Length; j++)
            {
                if(customAttributes[j] == PGFSerializeable) // THIS NOT WORK
                     Debug.Log(customAttributes[j]);