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

1. Coin Condition: The coin has a condition rating of 25 (BC), which indicates that it is in a fairly deteriorated state. This generally reduces its value compared to coins in better condition.

2. Previous Auction Prices: By observing the hammer prices of similar coins in the past, we can see that prices vary considerably. For example, in previous auctions, coins with higher conditions (such as 80 or 85) have reached hammer prices of up to 200 euros or more. However, coins in lower conditions (such as 30 or 40) have had hammer prices ranging between 50 and 90 euros.

3. Average Hammer Price: The average hammer price for similar coins is 131.21 euros, but this includes coins in better conditions.

4. Starting Price: The starting price for this coin is 30 euros, which suggests that the seller has moderate expectations about its value.

Given that the condition of this coin is quite low (25), and considering the hammer prices of coins in similar conditions, an estimated maximum purchase price could be between 40 and 70 euros. This is based on the fact that collectors may be willing to pay a little more than the starting price, but not enough to compete with coins in better conditions.

Therefore, an estimated maximum purchase price for this coin could be 60 euros.