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

1. Starting price: 40 euros.
2. Condition: The coin has a condition rating of 70 (VF-), indicating that it is in quite good shape.
3. Auction history: It has been auctioned 2 times in the past and sold on both occasions, suggesting that there is demand for this coin.
4. Average hammer price: 310 euros, indicating that, in general, coins of this reference tend to reach much higher prices than the starting price.
5. Previous prices: In the most recent auction, the coin was offered with a starting price of 80 euros and sold for 420 euros, showing significant interest and an increase in value.

Given that the condition of this coin is good and considering the auction price history, an estimated maximum purchase price could be in a range between the average hammer price and the starting price.

Taking all these factors into account, an estimated maximum purchase price could be around 350 to 400 euros. This is based on the interest shown in previous auctions and the condition of the coin.