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 condition. This generally increases its value compared to coins with lower conditions.

2. Auction History:
- The average hammer price for this coin in the past has been 20.83 euros.
- In previous auctions, hammer prices have varied, but some relevant examples are:
- In 2020, a coin with a condition rating of 100 was sold for 18 euros.
- In 2018, a coin with a condition rating of 95 was sold for 30 euros.
- In 2023, a coin with a condition rating of 95 was sold for 25 euros.

3. Starting Price and Estimates:
- The current starting price is 20 euros, which is a reasonable starting point.
- The average starting price in the past has been 13.32 euros, suggesting that the current starting price is higher than the historical average.

4. Sales Trends: The coin has been sold in 73.33% of the auctions it has participated in, indicating good demand.

Based on these factors, an estimated maximum purchase price could be between 25 and 30 euros, considering that the condition is high and there are precedents for sales in that range. Therefore, a reasonable maximum purchase price could be 30 euros.