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

1. Condition: The coin has a condition rating of 85 (ebc-), which is quite good. In the past, coins with a similar condition have reached auction prices that vary, but are generally found in a high range.

2. Previous auction prices: By looking at the auction prices of coins with a condition of 85, we can see that they have reached auction prices of up to 480 euros in recent auctions.

3. Starting price: The current starting price is 450 euros, indicating that the seller has expectations of a high auction price.

4. Price trends: The average auction price for this coin is 327.76 euros, but there are examples of much higher auctions, suggesting that there is potential for this coin to sell for a price above the average.

5. Auction history: The coin has been auctioned 88 times, with a high sales percentage (81 out of 88), indicating consistent demand.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 480-500 euros, as this is a price that has been reached in previous auctions for coins of similar condition and considering the current starting price.