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 quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Previous Prices: By looking at previous auction prices for coins with similar conditions (85 and 90), we can see that the auction price has varied. For example:
- In 2022, a coin with a condition of 85 was auctioned for 485 euros.
- In 2022, another coin with a condition of 95 was auctioned for 1000 euros, indicating that a higher condition can lead to significantly higher prices.

3. Starting Price and Average Auction Price: The current starting price is 700 euros, and the average auction price in previous auctions is 635.24 euros. This suggests that the starting price is aligned with the market value.

4. Auction Trends: The coin has been auctioned 23 times and has a history of successful sales, indicating a consistent interest in this reference.

5. Price Estimates: Based on the average auction price and the starting price, a reasonable auction price for a coin in condition 85 could be between 600 and 850 euros, considering that the starting price is 700 euros.

Given all this, an estimated maximum purchase price for this coin could be around 850 euros. This price reflects both the condition and the historical interest in the coin.