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

1. Condition of the coin: The coin to be auctioned has a condition of 85 (ebc-), which indicates that it is in fairly good shape, although it is not the best possible condition.

2. Previous auction prices: By looking at the hammer prices of coins with a similar condition (85) in the past, we can see that they have reached varying hammer prices. For example:
- In 2022, a coin with a condition of 85 was auctioned for 550 euros.
- In 2023, another coin with a condition of 85 was auctioned for 370 euros.

3. Average hammer price: The average hammer price for this particular coin is 314.98 euros, which gives us an idea of what buyers are willing to pay.

4. Starting price: The starting price of 350 euros is a good indicator of what is expected to be obtained at the auction.

5. Auction trends: The coin has been auctioned 45 times, of which 41 have been sold, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 400 to 550 euros, considering that the starting price is 350 euros and there are precedents of higher hammer prices for coins in similar conditions.

Therefore, a reasonable maximum purchase price could be 450 euros.