Based on the data provided, we can observe that the coin in question had a starting price of 12 euros in the most recent auction, with a conservation grade of 30 (BC+). Additionally, it has been auctioned in the past four times, with an average starting price of 50.2 euros and an average closing price of 100 euros.

The previous prices of this coin have varied, with a highest estimated price of 350 euros in a past auction. However, in the most recent auction, the closing price was 35 euros, below the estimated price of 25 euros.

Given that the coin will be auctioned soon and considering the historical data provided, we could estimate a maximum purchase price around 40-50 euros, taking into account the trend of previous prices and the conservation of the coin. It is important to note that the final price may vary depending on the demand at the auction and other external factors.