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

1. Current Condition: The coin has a grade of 25 (BC), which is relatively low. This will negatively affect its value compared to coins in better condition.

2. Auction History: By observing the hammer prices of coins with similar grades, we can see that the hammer prices for coins graded 25 have been quite low. For example, at the auction on January 18, 2023, a coin with a grade of 25 was sold for 25 euros.

3. Starting and Hammer Prices: The current starting price is 10 euros, and the average hammer price in the past has been 114.55 euros, but this includes coins in better condition.

4. Sales Trends: The coin has been auctioned 110 times, with a high sales percentage (99 out of 110). This indicates a consistent interest in this coin, although its condition may limit the price.

5. Comparison with Previous Prices: In the past, coins with a grade of 25 have had hammer prices ranging from 9 to 25 euros.

Given all this, an estimated maximum purchase price for this coin, considering its condition and price history, could be in the range of 25 to 30 euros. This reflects a price that could be attractive to a buyer, given the state of the coin and the interest in it.