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

1. Coin Condition: The coin has a condition rating of 90 (EBC), indicating 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 for coins with a similar condition (90), we can see that they have reached auction prices of up to 1000 euros in past auctions. However, there are also lower prices, such as 345 euros.

3. Starting Price and Average Hammer Price: The current starting price is 250 euros, and the average hammer price for this coin in the past has been 137.95 euros. This suggests that the starting price is relatively high compared to the average hammer price.

4. Auction Trends: The coin has been auctioned 168 times, with a 90% sell-through rate, indicating good demand. Additionally, there are 3 auctions scheduled in the coming days, which may influence competition and the final price.

5. Comparison with Recent Hammer Prices: In recent auctions, coins with similar conditions have reached hammer prices that vary, but some have exceeded 300 euros.

Taking all these factors into account, an estimated maximum purchase price for this coin could be between 350 and 450 euros. This is based on the good condition, historical demand, and previous hammer prices. However, the final price will depend on the competition in the auction and the willingness of other bidders to pay.