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 increases its value compared to coins with lower conditions.

2. Auction History:
- In the past, the coin has been auctioned 32 times, of which it has sold 22 times. This indicates good demand.
- Previous hammer prices for coins with similar condition (95) have reached up to 75 euros (in the auction on 2021-10-05).
- In the most recent auction (2024-09-19), the hammer price was 20 euros, suggesting that interest may have fluctuated.

3. Starting Price and Average Prices:
- The current starting price is 18 euros, and the average hammer price in the past has been 12.09 euros. However, the average starting price has been 12.29 euros, indicating that the current starting price is relatively high.

4. Price Trends:
- The price trend appears to be increasing, especially for coins in good condition. The last auction with a condition of 95 had a hammer price of 20 euros, suggesting that the market is willing to pay more for coins in this condition.

Based on these factors, an estimated maximum purchase price could be between 25 and 30 euros. This is based on the good condition of the coin and the demonstrated interest in previous auctions, as well as the highest recorded hammer price for similar coins.