To estimate a maximum purchase price for the coin in question, we can analyze the provided data, including auction history and previous hammer prices.

1. Current Condition: The coin has a condition rating of 85 (ebc-), indicating that it is in quite good shape. This is relevant because coins in better condition tend to fetch higher prices.

2. Price History:
- The average hammer price for this coin in the past is 785.45 euros.
- Previous hammer prices for coins with similar conditions (around 80-85) have varied, but there are examples of auctions reaching up to 1100 euros (in the case of a condition of 75).

3. Starting Price: The starting price is 500 euros, which is a reasonable starting point.

4. Auction Trends: Given that the coin has sold in all previous occasions and considering that the average hammer price is significantly higher than the starting price, this suggests that there is good demand for this coin.

5. Estimation: Based on the average hammer price and price history, a reasonable maximum purchase price could be in the range of 800 to 1000 euros, given that the condition is good and there are precedents for high hammer prices.

Therefore, an estimated maximum purchase price for this coin could be approximately 900 euros. This allows for some margin for competition in the auction and aligns with previous hammer prices.