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

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

2. Previous Auction Prices: By observing the hammer prices of coins with similar conditions, we can see that:
- In 2019, a coin with a condition of 90 was sold for 950 euros.
- In 2021, a coin with a condition of 95 was sold for 1300 euros.
- In 2022, a coin with a condition of 90 was sold for 800 euros.

3. Average Hammer Price: The average hammer price for this coin is 621.13 euros, but since the condition of the coin being auctioned is higher, we can expect the hammer price to be higher.

4. Starting Price: The starting price is 900 euros, indicating that the seller has expectations of a relatively high hammer price.

5. Market Trends: Given that the coin has been auctioned 43 times and has had a high sales percentage (40 out of 43), this suggests that there is consistent interest in this coin.

Taking all these factors into account, an estimated maximum purchase price could be between 1200 and 1500 euros, considering that the condition is high and there are precedents for sales in that range for coins of similar quality.