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. Previous Auction Prices: By looking at the hammer prices of coins with a similar condition (95), we find that:
- In 2020, a coin with a condition of 95 was auctioned for 800 euros.
- In 2019, another coin with the same condition sold for 644 euros.
- In 2014, a coin with a condition of 90 sold for 1100 euros.

3. Average Hammer Price: The average hammer price for this coin is 451.63 euros, which is also an important indicator.

4. Starting Price: The starting price is 450 euros, suggesting that the seller has expectations of a similar or higher hammer price.

5. Market Trends: Given that the coin has been auctioned 57 times and has had a high sales percentage (50 out of 57), this indicates a consistent interest in the coin, which may influence the price.

Based on these factors, an estimated maximum purchase price could be in the range of 800 to 1100 euros, considering that the condition is high and there are precedents for sales in that range. However, since the starting price is 450 euros, it is likely that the hammer price will not significantly exceed this value unless there is active competition among bidders.

Therefore, a reasonable estimated maximum purchase price could be 800 euros.