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

1. Condition: The coin has a condition rating of 85 (EF-), indicating that it is in quite good shape. Coins in this condition range typically command a higher price at auctions.

2. Starting Price: The starting price is 700 euros, which is a good indicator of the value the seller expects to obtain.

3. Price History: By looking at previous auction prices for coins with a similar condition (85), we can see that they have reached hammer prices that vary, but have occasionally exceeded 700 euros. For example, in past auctions, coins with a condition of 85 have reached hammer prices of up to 800 euros or more.

4. Market Trends: Given that the coin has been auctioned 89 times in the past and has had a high sell-through rate (87 out of 89), this suggests there is consistent interest in this coin, which may increase its value.

5. Recent Hammer Prices: In the most recent auctions, hammer prices for coins of similar condition have been in the range of 800 to 1000 euros.

Based on these factors, an estimated maximum purchase price for this coin could be between 800 and 900 euros, considering that the interest in the coin and its condition are favorable. However, it is important to keep in mind that the final price may vary depending on competition at the auction and other market factors at the time of sale.