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

1. Coin Condition: The coin to be auctioned has a condition rating of 90 (EBC), indicating that it is in very good condition. This generally translates to a higher price compared to coins with lower conditions.

2. Price History: By looking at the hammer prices of similar coins in the past, we can see that coins with a similar condition (90) have had varying hammer prices. For example, in previous auctions, coins with a condition of 90 have reached hammer prices of up to 150 euros.

3. Starting Price and Average Hammer Price: The starting price of 50 euros is reasonable, and the average hammer price of 47.86 euros suggests that, in general, coins of this reference sell close to this price. However, since the condition of this coin is higher, we can expect the hammer price to be higher.

4. Recent Trends: In the most recent auctions, hammer prices for coins of similar condition have shown an increase, which could indicate a rising trend in interest for these coins.

Based on these factors, an estimated maximum purchase price for this coin could be between 80 and 120 euros, considering that the condition is high and there is growing interest in this type of coin. A price of 100 euros could be a reasonable target for a buyer looking to secure the coin in a competitive auction.