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

1. Current Condition: The coin 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. Current Listing Price and Previous Prices: The current listing price is 125 euros, and the average hammer price in previous auctions is 128.37 euros. This suggests that the hammer price tends to be close to the listing price.

3. Sales History: The coin has been auctioned 71 times, of which it has sold 69 times. This indicates high demand and good interest in the coin.

4. Previous Hammer Prices: Looking at previous hammer prices for coins with similar conditions, we can see that they have reached prices of up to 420 euros in the past (in the case of a condition of 95). However, for conditions of 80-85, the hammer prices have been in the range of 75 to 150 euros.

5. Recent Trends: In the most recent auctions, hammer prices for coins with similar conditions have been in the range of 150 to 280 euros.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 150 to 200 euros. This is due to the good condition of the coin and the price trend in previous auctions. However, since the listing price is 125 euros, it is likely that the hammer price will not significantly exceed this range. Therefore, a reasonable maximum purchase price could be 200 euros.