To estimate a maximum purchase price for the coin in question, we can analyze the provided data, taking into account the current condition of the coin (70, VF-) and the hammer prices from previous auctions.

1. Condition: The coin has a condition of 70, which is considered VF-. This indicates that the coin is in an acceptable state, but it is not of high quality. In comparison, coins with higher grades (such as 80 or 95) have reached significantly higher hammer prices.

2. Previous hammer prices: Looking at the hammer prices of coins with similar conditions (70):
- In 2020, a coin with a condition of 70 was sold for 460 euros.
- In 2022, another coin with a condition of 70 was sold for 270 euros.
- In 2014, a coin with a condition of 70 was sold for 470 euros.

3. Average hammer price: The average hammer price for coins of this reference is 623.53 euros, but this includes coins in better condition.

4. Starting price: The current starting price is 350 euros, which suggests that the seller has moderate expectations.

5. Price trends: Since the coin has been sold every time it has been auctioned, this indicates a consistent interest in the coin, which may influence the price.

Based on these factors, an estimated maximum purchase price for the coin in condition 70 could be between 400 and 500 euros, considering that the highest hammer price for a coin of similar condition was 460 euros and that interest in the coin may lead to a price slightly above the starting price.

Therefore, a reasonable maximum purchase price could be 450 euros.