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

1. 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. Starting Price: The starting price is 1600 euros, which is an indicator of the seller's expectations.

3. Auction History:
- In 2020, the coin was estimated at 1300 euros and sold for 1110 euros with a condition of 85.
- In 2016, it was auctioned with a starting price of 750 euros, an estimated price of 900 euros, and sold for 1015 euros with a condition of 80.
- In 2015, although the condition value is not available, the final price was 800 euros.

4. Average Hammer Price: The average hammer price for this coin is 1218.75 euros, which provides a good reference point.

Given that the condition of the current coin is 85, which is similar to the auction in 2020, and considering the starting price of 1600 euros, a reasonable maximum purchase price could be in the range of 1200 to 1300 euros, since the average hammer price in the past has been 1218.75 euros.

Therefore, an estimated maximum purchase price could be 1300 euros. This is based on the condition, price history, and current starting price.