To estimate a maximum purchase price for the coin in question, let’s consider the following factors:

1. Starting Price: 30 euros. This is the initial price set for the auction.
2. Condition: The coin has a condition rating of 70 (VF-), indicating that it is in fairly good shape, although not the best possible condition. This may influence collectors' interest.
3. Auction History: The coin has been auctioned once in the past but did not sell, which may indicate that interest in this specific coin is limited. However, the fact that it has been auctioned suggests that there is some perceived value.
4. Average Hammer Price: There is no data on previous sales, making it difficult to establish an average hammer price.

Given that the coin has a starting price of 30 euros and considering its condition, an estimated maximum purchase price could be slightly higher than the starting price, but not too much, since it has not sold in the past.

Therefore, an estimated maximum purchase price could range between 30 and 50 euros, depending on collectors' interest at the time of the auction. A price of 40 euros could be a good benchmark, as it allows for some competition without exceeding the perceived value of the coin.