Based on the provided data, the coin will be auctioned with a starting price of 40 euros and is in a conservation grade of 70 (MBC-). In the past, this coin has been auctioned twice, both times it was sold, with an average starting price of 50 euros and an average closing price of 62.5 euros.

Additionally, we have a historical record of a previous auction of this same coin that took place on December 14, 2017, where the starting price was 60 euros, the estimated price was 90 euros, and the closing price was 65 euros, with an unspecified conservation grade.

Given that the conservation grade of the coin to be auctioned is 70 (MBC-) and considering the history of previous prices, we could estimate a maximum purchase price around 70-75 euros. It is important to note that the final price may vary depending on the demand at the auction and other factors that may influence buyers' decisions.