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

1. Condition: The coin has a condition rating 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 average hammer price in previous auctions is 79.13 euros, suggesting that, in general, coins of this reference tend to sell for significantly higher prices than the starting price.
- In past auctions, we have seen hammer prices vary, with some reaching up to 300 euros in 2011, although this may be an exceptional case.

3. Starting Price and Estimated Prices:
- The current starting price is 25 euros, which is relatively low compared to the average hammer price.
- The estimated price in previous auctions has varied, but there are examples where prices have been estimated at 40 to 50 euros.

4. Recent Trends:
- In the most recent auctions, the hammer price has been 40 and 120 euros for coins with the same condition, indicating a growing interest or an upward trend in the value of these coins.

Based on these factors, an estimated maximum purchase price could be in the range of 80 to 120 euros, considering the average hammer price and the condition of the coin. However, given the history of hammer prices, a reasonable maximum purchase price could be approximately 100 euros. This allows for competition in the auction and reflects the value of the coin's condition.