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

1. Coin Condition: The coin has a condition rating of 80 (MBC+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Previous Prices: By looking at the auction prices of coins with a similar condition (80), we can see that they have varied. For example:
- In a 2020 auction, a coin with a condition of 80 sold for 35 euros.
- In another 2020 auction, a coin with a condition of 80 sold for 70 euros.
- In 2022, a coin with a condition of 80 sold for 40 euros.

3. Average Hammer Price: The average hammer price for this coin is 56.41 euros, which can serve as a good indicator of the expected value.

4. Starting Price: The starting price is 65 euros, suggesting that the seller expects a reasonable price based on the current market.

5. Auction Trends: Given that the coin has been auctioned 199 times and has had a high sales percentage (171 out of 199), this indicates a consistent interest in this coin.

Based on these factors, an estimated maximum purchase price could be in the range of 70 to 90 euros, considering that the condition is good and the starting price is 65 euros. This also takes into account the possibility that buyers may be willing to pay a bit more for a coin in good condition.

Therefore, an estimated maximum purchase price could be 80 euros.