Based on the provided data, the coin in question has a conservation grade of 30 (BC+), indicating that it is not in the best condition but also not in the worst.

The starting price at the upcoming auction is 12 euros, with a historical average starting price of 41.83 euros. The historical average final auction price is 64.75 euros.

Considering the previous auction prices of this coin, where it has reached values of up to 250 euros, and taking into account that the conservation of the coin has been relatively consistent around 70-80, we could estimate a maximum purchase price around 90-100 euros.

It is important to note that the final auction price may vary depending on the demand at the auction and other factors that may influence buyers' decisions.