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

1. Current Condition: The coin has a condition rating of 85 (ebc-), which indicates that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price for this coin in the past is 456.7 euros.
- The last auction of this coin with a similar condition (85) had a hammer price of 600 euros.
- Overall, hammer prices have varied, but there are examples of auctions exceeding 600 euros, especially for coins in better condition.

3. Starting Price: The starting price is 300 euros, which may attract bidders, but the hammer price is usually significantly higher.

4. Price Trends: Looking at previous hammer prices, there is a trend for coins in good condition (like the one rated 85) to sell for above 600 euros.

Based on these factors, an estimated maximum purchase price for this coin could be between 600 and 750 euros, considering that the condition is good and the price history suggests that buyers are willing to pay more for coins in similar conditions.

Therefore, a reasonable maximum purchase price could be 750 euros.