CS0246 name 'Coin' could not be found (are you missing a using directive or an assembly reference?)

The type or namespace name 'Coin' could not be found (are you missing a using directive or an assembly reference?

public class ScinControl : MonoBehaviour
{
public int skinNum;
public Button buyButton;
public Image iLock;
public int price;
private Coin Coin;

public Sprite buySkin;
public Sprite equipped;
public Sprite equip;
public Sprite falseLock;
public Sprite trueLock;

public Image[] skins;

private void Start()
{
if (PlayerPrefs.GetInt("scin1" + "buy") == 0)
{
foreach (Image img in skins)
{
if ("scin1" == img.name )
{
PlayerPrefs.SetInt("scin1" + "buy", 1);
PlayerPrefs.SetInt("scin1" + "equip", 1);
}
else
{
PlayerPrefs.SetInt(GetComponent<Image>().name + "buy", 0);
}
}
}
}

private void Update()
{
if (PlayerPrefs.GetInt(GetComponent<Image>().name + "buy") == 0)
{
iLock.GetComponent<Image>().sprite = falseLock;
buyButton.GetComponent<Image>().sprite = buySkin;
}
else if(PlayerPrefs.GetInt(GetComponent<Image>().name + "buy") == 1)
{
iLock.GetComponent<Image>().sprite = trueLock;
if (PlayerPrefs.GetInt(GetComponent<Image>().name + "equip") == 1)
{
buyButton.GetComponent<Image>().sprite = equipped;
}
else if (PlayerPrefs.GetInt(GetComponent<Image>().name + "equip") == 0)
{
buyButton.GetComponent<Image>().sprite = equip;
}
}
}
public void buy()
{
if(PlayerPrefs.GetInt(GetComponent<Image>().name + "buy") == 0) {
if (Coin.Coin >= price)
{

iLock.GetComponent<Image>().sprite = trueLock;
buyButton.GetComponent<Image>().sprite = equipped;
Coin.Coin -= price;

PlayerPrefs.SetInt(GetComponent<Image>().name + "buy", 1);
PlayerPrefs.SetInt("skinNum", skinNum);
PlayerPrefs.SetInt("Coin", Coin.Coin);

foreach(Image img in skins)
{
if (GetComponent<Image>().name == img.name )
{
PlayerPrefs.SetInt(GetComponent<Image>().name + "equip", 1);
}
else
{
PlayerPrefs.SetInt( img.name + "equip", 0);

 private Coin Coin;