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

1. Condition of the coin: The coin being auctioned 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. Previous auction prices: By observing the hammer prices of coins with similar conditions, we can see that prices have varied. For example, in previous auctions, coins with conditions ranging from 80 to 85 have reached hammer prices between 40 and 480 euros, depending on demand and other factors.

3. Starting price and average hammer price: The current starting price is 125 euros, and the average hammer price in the past has been 81.34 euros. This suggests that the starting price is relatively high compared to the average hammer price.

4. Auction trends: The coin has been auctioned 66 times, of which 56 have been sold. This indicates a consistent interest in the coin, which may influence the hammer price.

5. Hammer prices of similar coins: In the past, coins with conditions of 80 have reached hammer prices of up to 480 euros, suggesting that there is significant potential for this coin to reach a high price, especially if there is interest in the auction.

Taking all these factors into account, an estimated maximum purchase price for this coin could be in the range of 200 to 300 euros. This range considers the good condition of the coin, the historical interest in it, and the current starting price. However, the final price will depend on the competition in the auction and the interest of collectors.