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

1. Current Condition: The coin is in a condition of 90 (EF), indicating that it is in good shape. This is a positive factor that can increase its value.

2. Auction History:
- The average hammer price for similar coins in the past is 127.92 euros.
- The coin has been auctioned 27 times, of which it has sold 25 times, indicating good demand.
- In previous auctions, coins with a similar condition (around 90) have reached hammer prices that vary, but some examples are:
- 240 euros in March 2023.
- 175 euros in March 2024.
- 200 euros in December 2023.

3. Starting Price and Average Starting Price:
- The starting price is 90 euros, and the average starting price is 98.7 euros. This suggests that the starting price is reasonable compared to the price history.

4. Recent Trends: Recent hammer prices for coins in similar conditions have been quite high, suggesting that there is growing interest in this type of coin.

Based on these factors, an estimated maximum purchase price could be between 200 and 250 euros, considering that the highest hammer price in the past has been 240 euros and that the condition of the coin is good. Therefore, a reasonable maximum purchase price could be 250 euros.