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

1. Current Condition: The coin has a condition of 75 (MBC), which indicates that it is in fairly good shape, but not of the best quality (FDC).

2. Auction History:
- It has been auctioned 9 times, of which it has sold 7 times. This indicates good demand.
- The average hammer price in previous auctions is 90.43 euros, suggesting that, in general, buyers are willing to pay close to this price.

3. Previous Prices:
- In the 2023 auction, the coin was estimated at 180 euros and sold for 290 euros, indicating a potential for high demand and that prices can vary significantly.
- In other auctions, hammer prices have ranged from 13 to 290 euros, depending on the condition and other factors.

4. Starting Price: The starting price is 25 euros, which is relatively low compared to the average hammer price.

Given that the coin's condition is 75 and considering the price history, an estimated maximum purchase price could be positioned in a range between the average hammer price and the highest recorded price.

Taking all these factors into account, an estimated maximum purchase price could be around 120-150 euros. This is based on the good condition of the coin and the interest shown in previous auctions.