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

1. Grade: The coin has a grade of 85 (ebc-), indicating that it is in fairly good condition, but not the best possible grade.

2. Previous auction prices:
- In previous auctions, we have seen hammer prices that vary significantly. For example, in 2020, a coin with a grade of 90 sold for 2000 euros, while another with a grade of 80 sold for 1000 euros.
- The average hammer price for similar coins has been 1396 euros, suggesting that the market is willing to pay close to this value for coins in similar conditions.

3. Current starting price: The starting price is 900 euros, which is a reasonable starting point.

4. Price trends: Looking at previous auctions, it seems that coins with similar grades have had hammer prices ranging from 1000 to 2000 euros, depending on demand and other factors.

Based on this data, an estimated maximum purchase price for this coin could be in the range of 1200 to 1600 euros. This is based on the fact that the grade is good, the starting price is reasonable, and previous hammer prices suggest there is potential to reach higher prices at auction.

Therefore, an estimated maximum purchase price could be 1500 euros.