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

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

2. Current Listing Price and Previous Prices: The current listing price is 1500 euros. In previous auctions, we have seen hammer prices that vary significantly, but there are examples of hammer prices exceeding 2000 euros, especially for coins in similar conditions.

3. Sales Trends: Out of the 25 times it has been auctioned, 22 have resulted in sales, indicating good demand. Additionally, the average hammer price in previous auctions is 646.1 euros, but there are several cases where the hammer price has been significantly higher.

4. Comparison with Previous Prices: In the 2014 auction, a coin with the same condition (85) sold for 2800 euros. This suggests that the market may be willing to pay high prices for coins in good condition.

5. Estimation Based on Historical Data: Given that the average hammer price has been 646.1 euros, but there are also examples of hammer prices exceeding 2000 euros, we can consider that the hammer price could be in a higher range due to the condition and demand.

Taking all these factors into account, an estimated maximum purchase price for this coin could be between 2000 and 3000 euros. This is based on the trend of previous prices and the current condition of the coin.