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 90 (EF), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Current Listing Price and Previous Prices: The current listing price is 375 euros. In previous auctions, coins with similar conditions (90) have had hammer prices that varied, but many have exceeded 300 euros. For example, in past auctions, the hammer price for coins with a condition of 90 has reached up to 380 euros.

3. Price Trends: The average hammer price for similar coins is 279.29 euros, but given that the condition of this coin is superior, it is reasonable to expect that the hammer price will be above this average.

4. Recent Hammer Prices: In the most recent auctions, hammer prices for coins of similar condition have ranged from 360 to 440 euros.

5. Sale Expectations: Given that there are 3 auctions scheduled in the coming days, this may increase competition and, therefore, the hammer price.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 400 to 450 euros. This reflects both the good condition of the coin and recent market trends.