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

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

2. Previous Auction Prices: By observing the hammer prices of coins with a similar condition (85) in previous auctions, we can see that the hammer prices have varied. For example:
- In a 2020 auction, a coin with a condition of 85 was sold for 40 euros.
- In another 2020 auction, the hammer price was 55 euros.
- In 2019, a coin with a condition of 85 was sold for 45 euros.

3. Average Hammer Price: The average hammer price for this coin is 52.34 euros, which is also a good indicator of the expected value.

4. Market Trends: Since the coin has been auctioned 137 times and has had a good number of sales (117), this suggests that there is consistent interest in this coin, which may increase its value.

5. Starting Price and Estimated Prices: The starting price is 25 euros, and the average starting price is 37.11 euros. This indicates that the market is willing to pay more than the starting price on many occasions.

Based on these factors, an estimated maximum purchase price for this coin could be between 60 and 80 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate. Therefore, a reasonable maximum purchase price could be 70 euros.