To estimate a maximum purchase price for the coin that will be auctioned, we will consider several factors, including the starting price, the condition of the coin, and the hammer prices of similar coins in the past.

1. Starting Price: 25 euros.
2. Condition of the Coin: 80 (MBC+), indicating good condition.
3. Previous Hammer Prices:
- In past auctions, coins with a similar condition (80) have reached hammer prices that varied considerably, but some relevant examples are:
- 190 euros (condition 80)
- 60 euros (condition 80)
- 55 euros (condition 80)
- 48 euros (condition 85)
- 42 euros (condition 85)

4. Price Trends: The average hammer price for similar coins is approximately 98.9 euros, suggesting that there is a market willing to pay more than the starting price.

5. Estimation: Given that the condition is good and there is a history of hammer prices exceeding the starting price, a reasonable maximum purchase price could be in the range of 80 to 120 euros, considering that the highest hammer price in the past was 190 euros.

Conclusion: An estimated maximum purchase price for this coin could be 100 euros. This is based on the good condition and the history of hammer prices, suggesting that buyers are willing to pay a price above the starting price.