Based on the provided data, we can observe that the coin in question had a starting price of 18 euros in the most recent auction, with a grade of 70 (MBC-). Additionally, it has been auctioned a total of 12 times in the past, with an average starting price of 33.25 euros and an average closing price of 71.42 euros.

When analyzing the previous prices of this coin, we can see that it has had significant variations in its starting, estimated, and closing prices throughout the previous auctions. For example, in the auction on 2020-10-21, it had a starting price of 60 euros, an estimated price of 100 euros, and a closing price of 110 euros, with a grade of 80. Whereas in the auction on 2017-03-16, it had a starting price of 110 euros, an estimated price of 200 euros, and a closing price of 320 euros.

Given that the grade of the coin in the most recent auction is 70 (MBC-), and considering the previous prices from past auctions, as well as the fact that it has been auctioned a total of 12 times, we could estimate a maximum purchase price around 80-90 euros for this coin in the next auction. It is important to note that the final price may vary depending on factors such as demand at the time of the auction and the competition from other bidders interested in the coin.