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 75 (MBC), indicating that it is in quite good shape. This may positively influence its value.

2. Current Listing Price and Previous Prices: The current listing price is 1200 euros, which is significantly higher than the starting and hammer prices from previous auctions. However, the hammer prices for coins with similar conditions (75) have ranged from 45 to 1100 euros.

3. Sales Trends: The coin has been auctioned 11 times in the past, of which it has sold 10 times. This indicates good demand and consistent interest in the coin.

4. Average Hammer Price: The average hammer price for similar coins is 154.6 euros, suggesting that the current listing price is quite high compared to the historical average.

5. Auction Expectations: Since it will be auctioned in the coming days and there is prior interest, this could drive the price up, but it is also important to consider that the listing price is quite elevated.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 600 to 800 euros. This range considers the good condition of the coin, historical demand, and the fact that the current listing price is quite high compared to previous hammer prices.