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

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating a medium-good quality. This is relevant because coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for coins with a similar condition (75) in the past has been approximately 25-35 euros, based on the provided data.
- There are examples of coins with a condition of 75 that have sold for prices ranging from 20 to 35 euros in previous auctions.

3. Starting Price and Average Hammer Price:
- The current starting price is 25 euros, and the average hammer price is 66.11 euros, suggesting that there is potential for the coin to sell at a higher price.

4. Recent Trends: In the most recent auctions, hammer prices for coins with similar conditions have shown a range of 25 to 50 euros, depending on demand and other factors.

Based on these points, an estimated maximum purchase price for this coin could be between 40 and 50 euros. This is based on the historical hammer price for coins of similar condition and the current market context.