Based on the provided data, we can observe that the coin has had an average auction closing price of 76.36 euros in previous auctions. Additionally, its condition has been described as "70 (MBC-)", indicating that it is in fairly good condition.

Considering that the starting price this time is 18 euros and the historical average closing price is 76.36 euros, we could estimate a maximum purchase price of around 80-85 euros for this coin in the upcoming auction. Given its good condition and past performance in auctions, this price range could be a realistic estimate for a successful purchase.