Based on the provided data, we can observe that the coin in question has had an average auction closing price of 82.33 euros in previous auctions. Additionally, the coin's condition has been described as "70 (MBC-)", indicating that it is in a fairly acceptable condition.

Considering that the starting price for the upcoming auction is 12 euros and the historical average starting price has been 35.13 euros, we can see that the closing price has been significantly higher in the past. Furthermore, the estimated price for the next auction is 120 euros.

Given that the coin has been sold in the past for prices higher than its current starting price, and considering its condition and the estimated price for the next auction, we could estimate a maximum purchase price around 100-120 euros. This takes into account that the historical closing price has been higher than the current estimated price and that the coin's condition is relatively good.

It is important to note that the final auction price may vary depending on the demand at that specific time, so it is advisable to monitor the auction to adjust the offer accordingly.