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

1. Starting price: 60 euros.
2. Average hammer price: 90 euros. This indicates that, in the past, the coin has had good interest and has reached a price higher than the starting price.
3. Condition: The coin has a condition rating of 70 (VF-), which suggests that it is in quite good shape, potentially increasing its value.
4. Auction history: It has been auctioned once and sold on that occasion, indicating that there is demand for this coin.

Given that the average hammer price is 90 euros and considering that the condition is good, an estimated maximum purchase price could be in the range of 90 to 120 euros. This is because, depending on demand and condition, collectors might be willing to pay a little more.

Therefore, an estimated maximum purchase price could be 100 euros. This allows for some margin for competition in the auction, but it is also based on the price history and the condition of the coin.