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

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. Historical Prices: By looking at previous auction prices for coins with a similar condition (85), we can see that auction prices have varied, but have generally remained in a range of 270 to 360 euros.

3. Starting Price and Average Hammer Price: The current starting price is 350 euros, and the average hammer price in the past has been approximately 272.63 euros. This suggests that the starting price is a bit higher than the previous average hammer price.

4. Recent Trends: In the most recent auctions, hammer prices for coins of similar condition have been in the range of 360 to 420 euros, indicating an upward trend.

5. Supply and Demand: The coin has been auctioned 336 times, with a sell-through rate of 97.3%, indicating strong demand.

Based on these factors, an estimated maximum purchase price for this coin could be around 400 euros. This is based on the recent trend of hammer prices and the condition of the coin. However, it is important to note that the final price may vary depending on competition in the auction and other market factors.