Based on the provided data, we can see that the coin in question has had a starting price in the current auction of 18 euros and is in a conservation grade of 70 (MBC-). Additionally, it has been auctioned in the past on several occasions, with closing prices ranging between 10 and 31 euros.

The average closing price of this coin in previous auctions has been 29.1 euros, with an average starting price of 19.55 euros. It is also noted that it has had an estimated price in the past ranging between 9 and 50 euros.

Given that the current conservation grade of the coin is 70 (MBC-) and considering the previous closing prices as well as the average closing price, the maximum estimated purchase price for this coin in the current auction could be around 35-40 euros. It is important to note that this is just an estimate and the final price may vary depending on the demand at the auction and other external factors.