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: Looking at previous auction prices, we can see that the coin has reached auction prices of up to 2800 euros in the past, although it has also had lower auction results. The average auction price in the past is 1646.82 euros.

3. Starting Price: The current starting price is 2000 euros, which is higher than the historical average auction price, suggesting that the seller has high expectations.

4. Sales Trends: The coin has sold in 11 of the last 13 auctions, indicating relatively good demand.

5. Comparison with Similar Conditions: In previous auctions, coins with similar conditions (such as 80 and 90) have had auction prices that varied, but generally sold for above 1500 euros.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 2000 to 2500 euros. This is based on the current condition, historical demand, and the starting price. A price of 2500 euros could be a reasonable limit, as it is above the starting price and aligns with previous auction prices for similar conditions.