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

1. Current Condition: The coin has a condition of 70 (VF-), indicating that it is in fairly good shape, but not the best possible condition.

2. Auction History:
- In 2017, the coin was auctioned with a starting price of 18 euros and sold for 40 euros, with a condition of 70.
- In 2024, it was auctioned with a starting price of 30 euros and sold for 120 euros, but with a condition of 80, which is better than the current one.

3. Average Hammer Price: The average hammer price for this coin is 40 euros, suggesting that, in general, buyers are willing to pay around that amount.

4. Current Starting Price: The starting price is 20 euros, which is relatively low compared to the average hammer price.

Given that the coin's condition is 70 and considering the auction history, an estimated maximum purchase price could be positioned in a range between the average hammer price and the highest hammer price observed.

Taking all this into account, a reasonable maximum purchase price could be approximately 60 euros. This is based on the fact that, although the condition is not the best, the interest in the coin seems to be strong, and the highest hammer price in the past suggests there is potential for a higher price in this auction.