Based on the provided data, we can see that the coin in question has a starting price of 15 euros and is in a conservation grade of 30 (BC+). Additionally, it has been auctioned four times in the past, with an average starting price of 31.25 euros and an average closing price of 52.5 euros.

We also have information on previous auctions of this same coin, where the starting and closing prices have varied. In the last auction recorded in February 2022, the coin was sold below the starting price, which could indicate a decrease in demand or interest in this particular reference.

Given that the conservation of the coin is relatively low (30 - BC+), and considering the fluctuation in previous auction prices, as well as the fact that the coin did not sell in the last auction, we could estimate a maximum purchase price around 40-45 euros. It is important to note that this is just an estimation and the final price could vary depending on factors such as demand at the time of the auction and competition from other bidders.