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

1. Condition of the coin: The coin has a condition rating of 90 (EBC), which indicates that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction history: By observing the hammer prices of coins with similar conditions (around 90-95), we can see that the hammer prices have varied, but there are examples of coins that have sold for significantly higher prices. For instance, in previous auctions, coins with a condition of 90 have reached hammer prices of up to 35 euros.

3. Average hammer price: The average hammer price for this coin is 27.36 euros, which provides a good reference.

4. Recent trends: In the most recent auctions, hammer prices for coins of similar condition have shown a range between 20 and 35 euros.

Based on these factors, an estimated maximum purchase price for the coin in question could be around 35 euros, considering that this price reflects both its condition and the recent auction history. However, it is important to keep in mind that the final price may vary depending on the competition in the auction and the demand at that time.