To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating that it is in acceptable shape, but not of the highest quality.

2. Auction History:
- The average hammer price for similar coins in the past has been 23.76 euros.
- In previous auctions, coins with a similar condition (75) have reached hammer prices of up to 30 euros (for example, in the auction on 2019-04-25).

3. Starting Price and Estimates:
- The current starting price is 20 euros, which is slightly lower than the average starting price of 21.34 euros.
- The estimated price for this auction is 25 euros, suggesting that there are expectations for the coin to sell for a reasonable price.

4. Sales Trends:
- Out of the 44 times this coin has been auctioned, it has sold 35 times, indicating a good sales rate.

Based on these factors, an estimated maximum purchase price could be around 30 euros, as this is a price that has been reached in previous auctions for coins of similar condition and aligns with the historical hammer price data. However, since the starting price is 20 euros, it is possible that it could be acquired for a price lower than this estimated maximum.