To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the current condition of the coin.

1. Current Condition: The coin has a condition of 75 (MBC), indicating that it is in a medium-low state of preservation. This is important because the auction price tends to be higher for coins in better condition.

2. Previous Auction Prices: By observing the auction prices of coins with a similar condition (75) and slightly better (80-85), we can see that:
- In previous auctions, coins with a condition of 75 have reached hammer prices of up to 60 euros (as in the auction on 2019-07-03).
- Coins with a condition of 80 have reached hammer prices of up to 45 euros (as in the auction on 2023-01-18).

3. Average Hammer Price: The average hammer price for this coin is 31.56 euros, which is also a good indicator.

4. Auction Trends: The coin has been auctioned 41 times, of which 28 have been successful sales. This suggests that there is a consistent interest in this coin.

5. Starting Price: The starting price is 18 euros, which is relatively low compared to previous hammer prices.

Based on this data, an estimated maximum purchase price could be set in a range between 40 and 60 euros, considering that the condition is 75 and there is a history of hammer prices that supports this estimate. A price of 50 euros could be a reasonable target, as it is in the middle of this range and takes into account the possibility of competition in the auction.