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

1. Current Condition: The coin has a condition of 70 (VF-), indicating that it is in relatively good shape. This can positively influence its value.

2. Auction History:
- The average hammer price in previous auctions is 67.38 euros.
- The coin has been auctioned 15 times, of which it has sold 13 times, indicating good demand.
- In previous auctions, hammer prices have varied, but there are examples of sales exceeding 100 euros, especially in higher conditions.

3. Starting Price and Average Starting Price:
- The current starting price is 25 euros, and the average starting price in the past has been 42.86 euros. This suggests that the current starting price is relatively low compared to the historical average.

4. Price Trends:
- In the most recent auction, the coin sold for 120 euros with a condition of 75, suggesting that there is potential for a higher price in similar conditions.

Based on these factors, an estimated maximum purchase price could be in the range of 80 to 100 euros, considering that the coin's condition is good and that the auction price history suggests it can reach higher values.

Therefore, a reasonable maximum purchase price could be 90 euros.