Based on the provided data, we can observe that the coin in question has had a starting price in the current auction of 120 euros and is in a conservation grade of 85 (ebc-). Additionally, it has been auctioned in the past on several occasions, with closing prices ranging between 30 and 600 euros.

The average closing price of this coin in previous auctions has been 128.81 euros, while the average starting price has been 81.41 euros. This indicates that the coin tends to reach prices higher than its starting price in auctions.

Considering that the conservation of the coin is good (85 ebc-) and it has performed well in previous auctions, we could estimate a maximum purchase price around 150-180 euros. This estimation is based on the upward trend of previous closing prices and the conservation quality of the coin.

It is important to note that the final auction price will depend on the demand at that specific moment, so it is advisable to monitor its evolution to adjust the offer accordingly.