To estimate a maximum purchase price for the coin in question, we can 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:
- The average hammer price in previous auctions is 74.33 euros.
- The coin has been auctioned 25 times, of which it has sold 17 times, indicating good demand.
- In previous auctions, hammer prices have varied significantly, with some reaching up to 270 euros in similar conditions.

3. Starting Price and Average Starting Price:
- The current starting price is 50 euros, and the average starting price in the past has been 57.22 euros. This suggests that the starting price is reasonable and could attract bidders.

4. Price Trends:
- Looking at previous hammer prices, there are examples of coins in similar conditions that have reached hammer prices of 66 euros, 60 euros, and 54 euros in recent auctions.

Taking all these factors into account, an estimated maximum purchase price for this coin could be in the range of 80 to 100 euros. This is based on the good condition of the coin, the hammer price history, and the demand observed in previous auctions.