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

1. Current Condition: The coin has a condition rating of 70 (VF-), indicating that it is in acceptable shape, but not among the best qualities. This can influence the price, as coins in better condition tend to fetch higher prices.

2. Auction History:
- The average hammer price for similar coins in the past is 42.11 euros.
- The coin has been auctioned 10 times, of which it has sold 9 times, indicating good demand.
- In previous auctions, hammer prices have varied, but there are examples of hammer prices reaching up to 100 euros for coins in better condition.

3. Starting Price and Average Starting Price:
- The current starting price is 18 euros, which is relatively low compared to the average starting price of 38.36 euros.

4. Recent Trends: In the most recent auction, the coin sold for 45 euros with a condition rating of 80, suggesting that there is growing interest in coins of acceptable quality.

Based on these factors, an estimated maximum purchase price could be in the range of 40 to 50 euros, considering that the condition is a limiting factor and that the average hammer price is 42.11 euros. Therefore, a reasonable maximum purchase price could be 45 euros.