Based on the data provided, we can observe that the coin in question has had a starting price of 25 euros in the current auction and is in a conservation grade of 70 (MBC-). Additionally, it has been auctioned 18 times in the past, with an average starting price of 109.53 euros and an average closing price of 161.41 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 previous auctions. However, overall, the closing prices have been higher than the starting and estimated prices in most cases.

Given that the current conservation grade of the coin is 70 (MBC-) and considering the trend of previous prices, as well as the fact that it has been successfully auctioned multiple times, we could estimate a maximum purchase price of around 80-90 euros for this coin in the current auction. It is important to note that this is just an estimate and the final price could vary depending on the demand at the auction.