To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the current condition of the coin.

1. Current Condition: The coin has a condition of 70 (VF-). This indicates that it is in an acceptable state, but not of high quality.

2. Previous Auction Prices:
- In 2019, a coin with a condition of 70 was auctioned for 220 euros.
- In 2021, another coin with a condition of 70 was auctioned for 267 euros.
- In 2020, a coin with a condition of 85 was auctioned for 320 euros.
- In 2020, a coin with a condition of 95 was auctioned for 550 euros.

3. Price Trends:
- The average auction price for coins auctioned in the past is 304.11 euros.
- The average starting price is 235 euros, suggesting that auction prices tend to be higher than starting prices.

4. Current Starting Price: The coin has a starting price of 275 euros.

Given that the condition of the coin is 70, and considering the previous auction prices for coins with a similar condition, an estimated maximum purchase price could be between 250 and 300 euros.

However, since the starting price is 275 euros, and considering that auction prices tend to be higher than the starting price, a reasonable maximum purchase price could be approximately 300 euros. This would allow for competitive bidding in the auction without exceeding a reasonable limit based on historical data.