To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating that it is in acceptable shape, but not in exceptional condition. This may influence the price, as coins in better condition tend to fetch higher prices.

2. Auction History:
- The average hammer price in previous auctions is 254.67 euros, suggesting that, in general, coins of this reference tend to sell close to this price.
- The most recent auction with a similar condition (75) had a hammer price of 351 euros, indicating that there is a market willing to pay more for coins in this state.

3. Starting Price: The current starting price is 250 euros, which is a good starting point. However, since the average hammer price is higher, it is reasonable to consider that the final price could be higher.

4. Sales Trends: Of the 12 times it has been auctioned, it has sold on 9 occasions, indicating good demand. Additionally, there have been no recent auctions scheduled, which could increase interest in this specific auction.

5. Comparison with Previous Prices: Previous hammer prices vary, but there are examples of auctions exceeding 600 euros in better conditions. This suggests that, although the current condition is 75, there is potential for a higher hammer price.

Taking all these factors into account, an estimated maximum purchase price could be around 350-400 euros. This is based on market interest, price history, and the current condition of the coin.