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

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating that it is in an acceptable state, but not among the best qualities.

2. Auction History:
- The coin has been auctioned 9 times, of which it has sold 8 times. This indicates a consistent interest in the coin.
- The average hammer price in previous auctions is 87.18 euros, which can serve as a reference.

3. Previous Prices:
- In previous auctions, the hammer prices for coins with similar conditions (75) have been 55 euros (in October 2022) and 110 euros (in November 2022). This suggests that the price can vary significantly depending on demand and other market factors.

4. Starting Price: The starting price is 50 euros, which is a reasonable starting point.

5. Recent Trends: In the most recent auctions, hammer prices have ranged from 55 to 100 euros for similar conditions.

Based on this data, an estimated maximum purchase price could be in the range of 90 to 110 euros, considering that the coin has a condition of 75 and has reached higher prices in the past. However, since the starting price is 50 euros, it is likely that buyers will be willing to pay a bit more, but not necessarily up to the historical maximum.

Therefore, a reasonable estimated maximum purchase price could be 100 euros.