To estimate a maximum purchase price for the coin that will be auctioned, we will consider several factors, including the coin's condition, previous auction prices, and the starting price.

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

2. Previous Auction Prices: By looking at the auction prices of coins with a similar condition (75) and within the condition range of 70 to 80, we can see that auction prices have varied. For example, in recent auctions, coins with a condition of 80 have reached auction prices of up to 190 euros, while others with a condition of 70 have had lower bids, around 30-50 euros.

3. Starting Price and Average Prices: The starting price of the coin is 20 euros, and the average auction price in the past has been approximately 98.9 euros. This suggests that there is significant potential for the coin to sell at a higher price than the starting bid.

4. Market Trends: Given that the coin has been auctioned 1,295 times in the past and has had a good sales percentage (971 out of 1,295), this indicates a consistent interest in this reference.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 80 to 120 euros, considering that the condition is good and there is a history of auction prices that supports this estimate. However, since the market can be volatile, it is advisable to keep an eye on the auction and adjust the bid accordingly.