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 85 (ebc-), which indicates that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Previous Prices: By looking at previous auction prices, we can see that the coin has had a price range that varies depending on the condition and demand at the time of the auction. For example:
- In 2014, it was auctioned for 390 euros with an unspecified condition.
- In 2015, the auction price was 240 euros.
- In 2024, it was auctioned for 380 euros with a condition of 70.
- In 2024, it was also auctioned for 420 euros with a condition of 85.

3. Average Auction Price: The average auction price for this coin is 314.29 euros, which provides a good reference for the expected value.

4. Starting Price and Average Starting Price: The current starting price is 275 euros, and the average starting price in the past has been 240 euros.

Given that the coin's condition is 85 and considering the previous auction prices, an estimated maximum purchase price could be set in a range above the average auction price, but it should also be reasonable in relation to the starting price.

Estimated Maximum Purchase Price: Based on the above information, a reasonable maximum purchase price could be between 400 and 450 euros, given that there are precedents for auctions in that range and the current condition is favorable.

Therefore, an estimated maximum purchase price could be approximately 420 euros.