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 the best possible condition.

2. Previous Auction Prices:
- In 2012, coins with a condition of 90 were auctioned, reaching hammer prices of up to 950 euros.
- In 2013, a coin with a condition of 75 was auctioned with a starting price of 192.94 euros, although the final hammer price is not reported.
- In 2016, a coin with a condition of 50 sold for 194.51 euros, indicating that the price can vary significantly with the condition.

3. Starting Price and Average Price:
- The current starting price is 70 euros, which is relatively low compared to the average starting price of 191.89 euros and the average hammer price of 488.17 euros.

4. Sales History: The coin has been auctioned 6 times, of which it has sold 4 times, suggesting a moderate interest in the coin.

Given that the condition of the coin is 75 and considering the hammer prices of similar coins in the past, an estimated maximum purchase price could be in the range of 200 to 300 euros. This is based on the fact that, although the condition is not the highest, the interest in the coin and previous hammer prices suggest that it could reach a higher price than the current starting price.

Therefore, an estimated maximum purchase price could be 250 euros.