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

1. Coin Condition: The coin to be auctioned has a condition of 75 (MBC), which indicates that it is in quite good shape.

2. Previous Prices: By looking at the hammer prices of coins with similar conditions, we can see that:
- In previous auctions, coins with conditions ranging from 70 to 80 have had hammer prices varying between 55 and 110 euros.
- For example, in the auction on 2022-10-18, a coin with a condition of 80 was sold for 110 euros.

3. Average Hammer Price: The average hammer price for this particular coin has been 91.56 euros, which is also a good indicator.

4. Starting Price: The starting price is 50 euros, suggesting that the auctioneer expects interest in the coin.

Given all this, an estimated maximum purchase price could be set in a range between 100 and 120 euros, considering that the condition is good and there are precedents for sales in that range for similar coins.

Therefore, a reasonable estimated maximum purchase price could be 110 euros.