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 75 (MBC), indicating that it is in quite good shape. This generally increases its value compared to coins with lower conditions.

2. Starting Price: The starting price is 110 euros, suggesting that the seller has high expectations for this auction.

3. Auction History: The coin has been auctioned once in the past, with a starting price of 30 euros and a hammer price of 30 euros. This indicates that, in the past, the coin did not have high demand, although the current starting price is significantly higher.

4. Average Hammer Price: The average hammer price in the past was 30 euros, suggesting that despite a higher starting price, the actual interest from buyers may be lower.

5. Auction Expectations: Since it will be auctioned again in the coming days, and considering that the starting price is 110 euros, it is possible that buyers may be willing to pay more than the previous average hammer price, but not necessarily the full starting price.

Taking all these factors into account, an estimated maximum purchase price could be positioned between the previous average hammer price and the current starting price. A reasonable range could be between 50 and 70 euros, considering that the condition is good and there is potential interest, but also that the auction history does not support a hammer price as high as the starting price.

Therefore, an estimated maximum purchase price could be 70 euros.