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

1. Current Condition: The coin has a condition of 85 (EF-), which indicates that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price for similar coins in condition 85 has been 70 euros in previous auctions.
- In the most recent auction, the hammer price was 86 euros for a coin with the same condition.

3. Starting Price and Average Hammer Price:
- The current starting price is 45 euros, which is reasonable given the price history.
- The average hammer price in the past has been 46.77 euros, suggesting that the hammer price could be in a similar range.

4. Price Trends:
- In previous auctions, hammer prices for coins with similar conditions have fluctuated, but they have shown a trend of increasing, especially in the most recent auctions.

Based on these factors, an estimated maximum purchase price could be between 80 and 90 euros, considering that the condition is good and that interest in quality coins tends to increase at auctions. Therefore, a reasonable maximum purchase price could be 90 euros.