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

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

2. Auction History:
- The average hammer price for coins of similar condition (75) has been approximately 38.58 euros.
- In previous auctions, hammer prices for coins with a grade of 75 have varied, but hammer prices of up to 59.68 euros have been seen in the past.

3. Current Starting Price: The starting price is 50 euros, which may influence bidder interest.

4. Recent Trends: In recent auctions, hammer prices have exceeded the starting price, suggesting that there is demand for this coin.

5. Comparison with Previous Prices: The coin has reached hammer prices of up to 85 euros in recent auctions, although in slightly better condition.

Taking all these factors into account, an estimated maximum purchase price could be around 60-70 euros. This is based on the historical hammer prices for coins of similar condition and the current interest in the coin. However, since the starting price is 50 euros, bidders may be willing to pay a little more, especially if there is competition in the auction.