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 is important because coins in better condition tend to fetch higher prices.

2. Starting Price and Average Hammer Price: The current starting price is 1300 euros, and the average hammer price in previous auctions is 1157.95 euros. This suggests that the starting price is aligned with sales expectations.

3. Sales History: The coin has been auctioned 22 times, of which it has sold 19 times. This indicates good demand and a history of successful sales.

4. Previous Prices: Looking at previous hammer prices for coins with a similar condition (85), we can see that they have reached prices of up to 2000 euros in recent auctions. However, there are also lower prices, suggesting that the market can be variable.

5. Recent Trends: In the most recent auctions, hammer prices have been quite high for coins in similar condition, which could indicate an upward trend in the value of these coins.

Based on these factors, an estimated maximum purchase price could be in the range of 1600 to 1800 euros, considering that the highest hammer price in the past for a coin of similar condition was 2000 euros, but also taking into account that the average hammer price is 1157.95 euros.

Therefore, a reasonable maximum purchase price could be 1700 euros.