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

1. Current 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 conditions.

2. Auction History:
- The average hammer price in previous auctions is 18.07 euros.
- The coin has been auctioned 20 times, of which it has sold 14 times, indicating good demand.
- In previous auctions, the hammer price has varied, but there are examples of sales reaching up to 35 euros (such as in the auction on February 5, 2015).

3. Starting Price and Estimates:
- The current starting price is 9 euros, and the average starting price is 9.53 euros. This suggests that the starting price is reasonable compared to the history.
- The estimated price for this auction is 20 euros, which is also a good indicator.

4. Price Trends:
- In recent auctions, the hammer price has been around 10-20 euros for coins of similar condition.

Based on these factors, an estimated maximum purchase price could be between 20 and 30 euros, considering that the condition is high and there is a price history that supports this estimate. Therefore, a reasonable maximum purchase price could be 25 euros.