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

1. Current Condition: The coin has a condition rating of 85 (ebc-), indicating 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. Previous Auction Prices: By looking at previous hammer prices, we can see that the coin has reached hammer prices that vary, but generally, the hammer prices have been in the range of 240 to 420 euros in recent auctions. The average hammer price is 316.8 euros.

3. Current Starting Price: The current starting price is 350 euros, indicating that the seller has expectations for the coin to sell at a reasonable price.

4. Price Trends: In the most recent auctions, hammer prices have been on the rise, suggesting a positive trend in the coin's value.

5. Previous Estimates: Estimated prices in previous auctions have been as high as 600 euros, indicating that there is potential for the coin to reach higher prices, especially if there is interest among collectors.

Taking all these factors into account, an estimated maximum purchase price could be around 400-450 euros. This range considers the current condition, previous hammer prices, and the upward trend in the coin's value.