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

1. 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:
- The average hammer price in previous auctions is 24.33 euros.
- In the most recent auction (2023-02-16), the coin was sold for 65 euros, suggesting that there is significant interest in high-condition coins.
- In other auctions, hammer prices have varied, but the highest recorded price is 65 euros.

3. Starting price: The current starting price is 18 euros, which is reasonable given the price history.

4. Market trends: Since the coin has been sold every time it has been auctioned, this indicates a steady demand.

Based on these factors, an estimated maximum purchase price could be in the range of 60 to 70 euros, considering that the highest recorded hammer price was 65 euros and that the coin's condition is high. This also takes into account the possibility that interest in the coin may have increased since the last auction.

Therefore, a reasonable maximum purchase price could be 70 euros.