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

1. Starting price: 250 euros.
2. Average hammer price: 360 euros. This is an important figure, as it indicates the average price at which the coin has sold in the past.
3. Condition: The coin has a condition rating of 70 (MBC-), which indicates that it is in good condition, although not the best possible (FDC).
4. Auction history: It has been auctioned once and sold on that occasion, suggesting that there is interest in the coin.

Given that the average hammer price is significantly higher than the starting price, and considering the good condition of the coin, an estimated maximum purchase price could be set between the average hammer price and an additional percentage to secure the purchase.

We could estimate a maximum purchase price around 400-450 euros, keeping in mind that interest in the coin may lead to competitive bidding. However, it is important to remember that the final price will depend on the demand at the auction and the bidding strategy of the participants.