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 80 (MS+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The coin has been auctioned 11 times, of which it has sold 4 times. This suggests that there is moderate interest in the coin.
- The average hammer price in previous auctions is 52.47 euros, which can serve as a good indicator of market value.

3. Starting and Hammer Prices:
- Starting prices have varied, but there are examples of hammer prices exceeding the starting price, indicating that buyers are willing to pay more in some cases.
- The current starting price is 50 euros, which is slightly below the average hammer price.

4. Price Trends:
- In previous auctions, hammer prices have ranged between 45 and 61.88 euros, suggesting that the hammer price may be in a similar range.

Based on these factors, an estimated maximum purchase price could be around 60-65 euros. This is based on the hammer price history and the good condition of the coin. However, it is important to note that collector interest and competition in the auction can also influence the final price.