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

1. Current Condition: The coin has a condition rating of 95 (EF+), indicating that it is in very good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Current Listing Price and Previous Prices: The current listing price is 150 euros. In previous auctions, the highest hammer price for a coin with a similar condition (95) was 170 euros in 2018. However, lower hammer prices have also been observed in other auctions.

3. Sales Trends: Out of the 23 times it has been auctioned, it has sold 17 times, indicating good demand. The average hammer price in previous auctions is 88.59 euros, but this includes coins of different conditions.

4. Estimated Price: The estimated price for the current auction is 300 euros, suggesting that there are expectations for the coin to reach a higher price due to its condition.

5. Comparison with Historical Prices: Considering that a condition rating of 95 is quite high and that the highest hammer price in the past was 170 euros, it is reasonable to think that the price could be in a higher range than in previous auctions.

Taking all these factors into account, an estimated maximum purchase price could be between 200 and 250 euros. This is based on the good condition of the coin and the price trends in previous auctions, as well as the current estimated price.