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

1. Current Condition: The coin has a condition of 25 (BC), which indicates that it is not in very good shape. This generally reduces its value compared to coins in better condition.

2. Previous Prices: By looking at previous auction prices, we can see that coins with similar conditions have had varying auction prices. For example:
- In 2022, a coin with a condition of 30 was auctioned for 90 euros.
- In 2022, another coin with a condition of 75 was auctioned for 70 euros.
- In 2024, a coin with a condition of 70 was auctioned for 120 euros.

3. Average Auction Price: The average auction price for this coin is 113.22 euros, but this includes coins in better conditions.

4. Starting Price and Average Starting Price: The starting price is 70 euros, and the average starting price is 74.03 euros. This suggests that the market is willing to start the auction at a relatively low range.

5. Sales Trends: The coin has been auctioned 31 times, of which it has sold 27 times. This indicates good demand in the market.

Given that the condition of the coin is low (25), and considering the auction prices of coins with similar conditions, an estimated maximum purchase price could be in the range of 50 to 70 euros. However, since the starting price is 70 euros, it is reasonable to consider that the maximum purchase price could be slightly above this, but not much more, given the condition.

Estimated Maximum Purchase Price: 70 euros.