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. Auction History:
- The average hammer price for similar coins has been 41.15 euros.
- In previous auctions, coins with a similar condition (90) have reached hammer prices that vary, but some examples are:
- 14 euros (2020-12-14)
- 30 euros (2020-10-20)
- 65 euros (2020-05-26)
- 220 euros (2020-12-17, although this coin had a condition of 100).

3. Starting Price and Estimated Prices:
- The current starting price is 12 euros, and the average starting price in the past has been 25.53 euros. This suggests that the current starting price is relatively low compared to the historical average.

4. Recent Trends: In the most recent auctions, hammer prices have shown a trend of increasing, especially for coins in good condition.

Based on these factors, an estimated maximum purchase price for this coin could be between 50 and 70 euros, considering its good condition and the history of hammer prices. This would allow for competitive bidding in the auction without exceeding a reasonable limit based on historical data.