To estimate a maximum purchase price for the coin that is going to be auctioned, we can consider several factors:

1. Condition of the coin: The coin in question has a condition rating of 95 (EF+), which indicates that it is in very good condition. This generally translates to a higher price compared to coins with lower condition ratings.

2. Previous auction prices: By looking at the hammer prices of coins with a similar condition (95), we can see that in the past, a coin with this condition sold for 480 euros in 2019. This is a key piece of information, as it sets a precedent for the value of the coin.

3. Starting price and average prices: The current starting price is 300 euros, and the average hammer price for similar coins is 78.67 euros. However, since the condition of this coin is significantly better, it is reasonable to expect that the hammer price will be higher.

4. Auction trends: Given that the coin has been auctioned 81 times in the past and has sold 75 times, there is good demand for this coin, which may drive up its price.

Based on these factors, an estimated maximum purchase price could be in the range of 450 to 550 euros, considering that the highest hammer price in the past was 480 euros and that the current condition is very good. This also takes into account the starting price of 300 euros, which is reasonable for a coin of this quality.

Therefore, an estimated maximum purchase price could be 550 euros.