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-), which indicates that it is in fairly good shape, but not the best possible condition. This can influence the price, as coins in better condition tend to fetch higher prices.

2. Auction History:
- It has been auctioned 6 times in the past, of which 3 have been successful sales.
- The average hammer price in previous auctions is 35.33 euros, indicating that, in general, buyers are willing to pay more than the starting price.

3. Starting and Hammer Prices:
- The current starting price is 9 euros, which is relatively low compared to the average hammer price of 35.33 euros.
- In previous auctions, hammer prices have varied, but there are examples where prices have reached 75 euros (in 2017).

4. Recent Trends: In the most recent auctions, hammer prices have been in the range of 15 to 16 euros for coins in superior conditions (such as condition 100).

Given all this, an estimated maximum purchase price could be set in a range between 35 and 50 euros, considering that the current condition is good, but not excellent, and that the starting price is low. This also takes into account the history of hammer prices in previous auctions.

Therefore, a reasonable maximum purchase price could be 45 euros.