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 quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History: By looking at previous hammer prices for coins with similar conditions, we can see that:
- In past auctions, coins with a condition of 85 have reached hammer prices of up to 240 euros (as seen in the auction on 2018-04-25).
- The average hammer price for coins of similar condition seems to be around 90-150 euros.

3. Starting Price and Average Hammer Price: The current starting price is 45 euros, and the average hammer price in the past has been approximately 67.97 euros. This suggests that the hammer price could be significantly higher than the starting price.

4. Recent Trends: In the most recent auctions, the hammer price has shown an increase, which could indicate a rising trend in interest for this coin.

Based on these factors, an estimated maximum purchase price for this coin could be between 150 and 200 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate. However, given the market context and demand, a price of up to 240 euros could be achievable in a competitive auction.

Therefore, a reasonable maximum purchase price could be 200 euros.