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

1. Condition: The coin has a condition rating of 75 (MBC), indicating that it is in quite good shape. This generally increases its value compared to coins in lower condition.

2. Auction History:
- It has been auctioned 11 times in the past, of which it has sold 8 times. This suggests there is consistent interest in the coin.
- The average hammer price in previous auctions is 37 euros, which can serve as a good indicator of market value.

3. Previous Auction Prices:
- In the 2018 auction, with a condition of 75, the coin sold for 65 euros, which is a good benchmark.
- In other auctions, hammer prices have varied, but the highest recorded price for a similar condition is 65 euros.

4. Starting Price: The current starting price is 50 euros, which is reasonable given the price history.

Based on these factors, an estimated maximum purchase price could be between 65 and 80 euros, considering that the condition is good and that interest in the coin appears to be solid. However, since the highest hammer price in the past was 65 euros, a maximum purchase price of around 70 euros could be a prudent estimate.