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

1. Coin Condition: The coin has a condition rating of 95 (S/C-), indicating that it is in very good shape. This generally translates to a higher price compared to coins with lower condition ratings.

2. Auction History:
- The average hammer price for coins with a similar condition (95) has been 75 euros in a previous auction (2020-12-17).
- In other auctions, hammer prices for coins with a condition of 95 have varied, but the range has generally been high, with hammer prices reaching up to 40-75 euros.

3. Starting Price and Average Hammer Price:
- The current starting price is 15 euros, which is relatively low compared to previous hammer prices.
- The average hammer price in the past has been 17.17 euros, suggesting that the final hammer price could be higher than the starting price.

4. Recent Trends: In the most recent auctions, hammer prices for coins with a condition of 95 have shown a range of 30 to 40 euros, indicating that there is a steady demand for coins in good condition.

Based on these factors, an estimated maximum purchase price for this coin could be between 40 and 75 euros, considering that the condition is high and there is a history of hammer prices that supports this estimate.

Therefore, a reasonable maximum purchase price could be 75 euros.