To estimate a maximum purchase price for the coin in question, we can analyze the provided data, including the auction history 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. In the history, coins with similar conditions have had varying hammer prices.

2. Price History:
- In previous auctions, coins with a condition of 70 have had hammer prices of 300 (2020-11-19) and 340 (2022-03-17).
- The coin with a condition of 85 sold for 500 (2020-01-23), indicating that an improvement in condition can significantly increase the price.
- The coin with a condition of 95 sold for 700 (2022-10-19) and 900 (2023-03-16), showing that coins in better condition have a considerably higher value.

3. Starting Price and Average Hammer Price:
- The current starting price is 350 euros, and the average hammer price in the past has been 457.85 euros. This suggests that the hammer price could be in a similar range or slightly above the starting price.

4. Estimation:
- Given that the condition is 70 and considering the previous hammer prices for coins with similar conditions, a reasonable hammer price could be between 300 and 400 euros.
- However, since the starting price is 350 euros, and considering that there has been interest in coins of this reference, a maximum purchase price could be a bit higher, perhaps in the range of 400 to 450 euros.

Conclusion: Based on the analysis, an estimated maximum purchase price for this coin could be 450 euros.