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

1. Current Condition: The coin has a condition rating of 70 (VF-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price in previous auctions is 669.22 euros.
- In past auctions, we have seen hammer prices that varied significantly, ranging from 200 euros to 1600 euros, depending on the condition and other factors.

3. Starting Prices and Estimates:
- The current starting price is 300 euros, which is relatively low compared to the average hammer price.
- The average starting price in previous auctions is 382.92 euros, suggesting that the current starting price is in line with expectations.

4. Price Trends:
- In the most recent auction of 2024, the coin was auctioned with a starting price of 300 euros and a hammer price of 350 euros, indicating that there is interest in the coin, although the hammer price was relatively low.

5. Comparison with Similar Coins:
- In the 2022 auction, a coin with a similar condition (70) sold for 420 euros, which can serve as a reference.

Taking all these factors into account, an estimated maximum purchase price for the coin could be between 500 and 700 euros. This is based on the history of hammer prices and the current condition of the coin. A price of 600 euros could be a reasonable target, as it aligns with previous estimates and the interest shown in past auctions.