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

1. Current Condition: The coin has a condition of 85 (ebc-), which indicates 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 similar conditions (85 and 90), we can see that auction prices have varied. For example:
- In previous auctions, coins with a condition of 85 have reached hammer prices of up to 300 euros.
- Coins with a condition of 90 have reached hammer prices of up to 400 euros.

3. Starting Price and Average Hammer Price: The current starting price is 300 euros, and the average hammer price in the past has been 303.31 euros. This suggests that the market is willing to pay around this price.

4. Recent Trends: In the most recent auctions, hammer prices have shown a trend of increasing, especially for coins in good condition.

Based on these factors, an estimated maximum purchase price for this coin could be between 350 and 400 euros. This is because, although the condition is not the highest, the interest in good quality coins and the price trend in the market suggest that buyers may be willing to pay a little more than the previous average hammer price.

Therefore, a reasonable maximum purchase price could be approximately 375 euros.