Based on the data provided, we can observe that the coin has had an average auction closing price of 31.69 euros in previous auctions. Additionally, the current condition of the coin is 85 (ebc-), indicating that it is in fairly good condition.

Considering that the starting price in this auction is 18 euros and the historical average closing price is 31.69 euros, we could estimate a maximum purchase price around 35-40 euros. Given that the coin has performed well in previous auctions and its condition is high, collectors may be willing to pay slightly more than the average closing price.

Therefore, an estimated maximum purchase price for this coin in the upcoming auction could be around 35-40 euros. It is important to note that the final value will depend on the demand at the auction and the willingness of participants to bid on it.