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 quite good shape. This generally translates to a higher price compared to coins in lower condition.

2. Auction History:
- The average hammer price for similar coins in the past is 315.21 euros.
- The last auction for this coin had a hammer price of 420 euros, suggesting that there is growing interest in this coin.
- Previous auctions show that the hammer price has varied, but it has reached up to 560 euros under similar conditions.

3. Starting Price and Average Starting Price:
- The current starting price is 350 euros, which is slightly higher than the average starting price of 261.05 euros. This may indicate that the seller is confident that the coin will reach a higher price.

4. Recent Trends: Recent auctions have shown an increase in hammer prices, which may indicate an upward trend in the value of this coin.

Based on these factors, an estimated maximum purchase price could be in the range of 400 to 500 euros. This is due to the good condition of the coin, the interest shown in recent auctions, and the hammer price history.

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