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

1. Condition: The coin has a condition rating of 85 (ebc-), which indicates that it is in fairly good shape, but not the best possible condition. This can influence the price, as coins in better condition tend to fetch higher prices.

2. Starting price and previous prices: The current starting price is 1400 euros. In previous auctions, the average hammer price has been 1453.33 euros, suggesting that buyers are willing to pay a bit more than the starting price on average.

3. Auction history: The coin has been auctioned 9 times in the past, of which it has sold 7 times. This indicates a consistent interest in the coin, which can increase its value.

4. Previous hammer prices: In the most recent auction, the hammer price was 1800 euros, suggesting that there is potential for the price of this coin to increase in the future.

5. Price trends: The average starting price in previous auctions has been 1133.75 euros, indicating that the current starting price is higher than the historical average, but also reflects an increase in interest or value of the coin.

Taking all these factors into account, an estimated maximum purchase price could be around 1600-1700 euros. This range considers the interest in the coin, its condition, and the history of hammer prices, allowing for some margin for competition in the auction.