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. Previous auction prices: By looking at the hammer prices from previous auctions for coins with a similar condition (95 or 100), we can see that the hammer prices have varied, but there are recent examples showing hammer prices of up to 400 euros.

3. Current starting price: The starting price is 400 euros, which is a good indicator of the seller's expectations. However, the starting price does not always translate into the final hammer price.

4. Sales trends: The coin has been auctioned 66 times in the past, of which it has sold 60 times. This indicates good demand and a history of successful sales.

5. Average prices: The average hammer price in the past has been 253.48 euros, suggesting that while there is potential to reach higher prices, the hammer price tends to be below the starting price.

Given all this, an estimated maximum purchase price could be in the range of 400 to 480 euros, considering that there have been recent auctions in that range and that the coin's condition is high. However, it is important to keep in mind that the final price will depend on the competition in the auction and the interest of other buyers.

Therefore, a reasonable maximum purchase price could be 480 euros.