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

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

2. Previous Auction Prices: By observing the hammer prices of coins with similar conditions (75 and 70), we can see that the hammer prices have varied. For example:
- In 2018, a coin with a condition of 75 was auctioned for 95 euros.
- In 2019, a coin with a condition of 70 was auctioned for 50 euros.
- In 2020, a coin with a condition of 70 was auctioned for 50 euros.

3. Average Hammer Price: The average hammer price for this coin is 166.58 euros, suggesting that there is significant interest in this coin.

4. Starting Price and Average Starting Price: The starting price is 50 euros, and the average starting price is 65.53 euros. This indicates that the starting price is relatively low compared to the average hammer price.

5. Auction Trends: Since it has been auctioned 123 times and sold 109 times, this indicates that the coin has a good sell-through rate, which may increase competition and, therefore, the price.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 200 euros, considering that the condition is good and there is interest in the coin. However, since the average hammer price is 166.58 euros, a reasonable maximum purchase price could be approximately 180 euros.