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 relatively good shape, but not the best possible condition.

2. Starting Price and Average Hammer Price: The starting price is 130 euros, and the average hammer price in previous auctions is 169.42 euros. This suggests that, generally, coins of this reference tend to sell for above their starting price.

3. Sales History: The coin has been auctioned 21 times, of which it has sold 19 times. This indicates good demand and consistent interest in this coin.

4. Previous Prices: Looking at previous hammer prices for coins with similar conditions (70-85), we can see that they have reached hammer prices ranging from 51 to 420 euros, depending on the condition and other factors.

5. Recent Trends: In the most recent auctions, hammer prices have been quite high, especially for coins in condition 85, which have reached up to 420 euros.

Given that the condition of the coin in question is 75, and considering the average hammer price of 169.42 euros, an estimated maximum purchase price could be in the range of 180 to 220 euros. This is based on the trend that coins in similar conditions have reached hammer prices that exceed the starting price and approach 200 euros.

Therefore, an estimated maximum purchase price for this coin could be 200 euros.