To estimate a maximum purchase price for the coin in question, we can consider several factors:

1. Coin Condition: The coin to be auctioned has a condition rating of 90 (EBC), indicating that it is in quite good shape.

2. Previous Prices: By looking at the hammer prices of coins with similar conditions (around 90), we can see that they have reached hammer prices that vary, but generally, the hammer prices for coins in similar conditions have been in the range of 150 to 250 euros in recent auctions.

3. Average Hammer Price: The average hammer price for this coin is 109.05 euros, suggesting that, in general, coins of this reference tend to sell for above this price.

4. Starting Price: The starting price is 90 euros, which is a good starting point, but given that the coin is in good condition, it is likely that the hammer price will be significantly higher.

5. Auction Trends: Since there have been 107 auctions of this coin and 85 of them have sold, there is good demand, which may drive up the hammer price.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 200 to 250 euros, considering that the condition is good and that interest in the coin appears to be high. However, it is important to keep in mind that the final price may vary depending on competition in the auction and other market factors at the time of sale.