To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

1. Current Condition: The coin has a condition rating of 85 (ebc-), indicating that it is in fairly good shape, but not the best possible condition.

2. Previous Prices: Looking at previous auction prices for coins with a similar condition (85), we can see that they have reached auction prices of up to 440 euros (in the March 2020 auction) and 400 euros on several more recent occasions.

3. Average Auction Price: The average auction price for this coin is 338.66 euros, which gives us an idea of what buyers are willing to pay on average.

4. Starting Price: The starting price is 325 euros, which is a good starting point, but does not necessarily indicate the final auction price.

5. Recent Trends: In the most recent auctions, the auction prices have been in the range of 380 to 420 euros for similar conditions.

Based on these factors, an estimated maximum purchase price could be in the range of 400 to 450 euros, considering that the condition is good and there is a history of auction prices that supports this estimate. Therefore, a reasonable maximum purchase price could be 450 euros.