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 that it is in an acceptable state, but not among the best conditions.

2. Auction History:
- The average hammer price in previous auctions is 256.8 euros.
- In past auctions, the coin has reached hammer prices of up to 1100 euros (in the case of the December 2020 auction), although this was for a coin in better condition (condition rating 100).
- The majority of previous auctions with a similar condition (75) have had hammer prices ranging between 12 and 30 euros, with a highest price of 41 euros in a 2021 auction.

3. Starting Price: The current starting price is 25 euros, which is relatively low compared to the average hammer price.

4. Sales Trends: The coin has been sold in 66.67% of the auctions it has participated in, suggesting there is a consistent interest in this coin.

Based on these factors, an estimated maximum purchase price could be set in a range between 30 and 50 euros, considering that the condition is 75 and the starting price is 25 euros. This would allow for a competitive offer without exceeding the market value observed in previous auctions for coins in similar conditions.

Therefore, a reasonable maximum purchase price could be 40 euros.