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

1. Current Condition: The coin has a condition rating of 85 (MBC+/EBC-), indicating that it is in quite good shape. This is important because coins in better condition tend to fetch higher prices.

2. Auction History:
- The average hammer price in previous auctions is 170.56 euros.
- The last auction with a similar condition (85) had a hammer price of 150 euros.
- In other auctions, hammer prices have varied, but the highest values have reached up to 300 euros in superior conditions.

3. Starting Price: The current starting price is 175 euros, which is slightly higher than the previous average hammer price.

4. Sales Trends: The coin has been auctioned 11 times, of which it has sold 10 times, indicating good demand.

5. Projections: Given that there is an auction scheduled in the coming days, interest in the coin may increase, potentially raising the hammer price.

Based on these factors, an estimated maximum purchase price could be in the range of 200 to 250 euros, considering that the condition is good and that interest in the coin may be high. This also takes into account the starting price and the hammer price history in similar conditions.

Therefore, a reasonable maximum purchase price could be 250 euros.