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

1. Current Condition: The coin has a condition rating of 70 (VF-), indicating that it is in relatively good shape, but not of the highest quality (UNC).

2. Auction History:
- The average hammer price in previous auctions is 97.75 euros.
- The coin has been auctioned 17 times, of which it has sold 9 times. This suggests there is moderate interest in the coin.
- Previous hammer prices varied, but there are examples of hammer prices exceeding 80 euros, even reaching up to 325 euros in the case of a condition rating of 90.

3. Starting Price: The current starting price is 40 euros, which is relatively low compared to the average hammer price.

4. Price Trends: In recent auctions, the hammer price has been around 85-140 euros, suggesting there is potential for a higher hammer price in this auction.

Given all this, an estimated maximum purchase price could be in the range of 80 to 120 euros, considering that the condition is 70 and that interest in the coin seems to be moderate. A price of 100 euros could be a reasonable target, as it aligns with the average hammer price and the price trend in previous auctions.

Therefore, the estimated maximum purchase price could be 100 euros.