Based on the data provided, we can observe that the coin in question had a starting price in the current auction of 15 euros, with a conservation grade of 30 (BC+). Additionally, it has been auctioned in the past 9 times, with an average starting price of 85 euros and an average closing price of 148.33 euros.

When analyzing the previous prices of this coin, we can see that it has had variations in its starting, estimated, and closing prices throughout the previous auctions. The conservation grade of the coin has been valued at 75, 70, and 85 in previous auctions.

Given that the coin has been sold in all previous auctions, and considering the upward trend in closing prices, as well as the conservation grade of the coin, we could estimate a maximum purchase price around 160-170 euros. This is considering that the coin is in an acceptable conservation grade and has performed well in previous auctions.