To estimate a maximum purchase price for the coin in question, we can analyze 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. Auction History:
- The coin has been auctioned 9 times, of which it has sold 6 times. This suggests that there is consistent interest in the coin.
- The average starting price in previous auctions is 68.48 euros, and the average hammer price is 66.16 euros. This provides context regarding the market value of the coin.

3. Previous Prices:
- Previous hammer prices varied, but there is a notable price of 93.81 euros in 2013 for a coin with the same condition (85).
- There is also a hammer price of 80 euros in 2015 for a coin with a condition of 90, indicating that the price may be sensitive to condition.

4. Current Starting Price: The starting price is 80 euros, which is a good starting point.

Given that the condition of the coin is good (85) and considering the previous hammer prices, an estimated maximum purchase price could be in the range of 90 to 100 euros. This is based on historical interest and the current condition.

Therefore, an estimated maximum purchase price could be 95 euros.