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

1. Condition: The coin to be auctioned has a condition of 95 (S/C-), indicating that it is in very good shape. This generally increases its value compared to coins of lower condition.

2. Previous auction prices:
- In the December 2021 auction, a coin with a condition of 95 sold for 55,000 euros, suggesting that the market is willing to pay a high price for coins in excellent condition.
- In other auctions, hammer prices have varied, but the average hammer price for coins of similar condition has been approximately 30,700 euros.

3. Starting price and estimates:
- The starting price of 25,000 euros is reasonable, but given the history of hammer prices, the final price may be significantly higher.
- The average hammer price of 30,700 euros also suggests that the selling price could be in a similar range.

4. Market trends: Since the coin has been auctioned several times and has had considerable interest, it is likely that the hammer price will remain at a high level.

Taking all these factors into account, an estimated maximum purchase price could be between 50,000 and 60,000 euros, especially if there is competitive interest in the auction. This is based on the highest recorded hammer price and the condition of the coin.