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

1. Current Condition: The coin has a condition rating of 70 (VF-), indicating that it is in acceptable condition, but not among the best qualities. This may influence the price, as coins in better condition tend to fetch higher prices.

2. Auction History:
- The average hammer price for similar coins has been 548.75 euros.
- In previous auctions, hammer prices have varied, but there are examples of coins with similar condition that sold for 300 euros (2020) and 320 euros (2021).
- There are also examples of coins in better condition (condition 90 and 95) that have reached significantly higher hammer prices (400 to 1600 euros).

3. Starting Price: The starting price is 350 euros, which may be a good indicator of initial interest in the coin.

4. Price Trends: Observing previous hammer prices, it seems there is potential for price increase depending on demand at the auction.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 400 to 600 euros. This is based on the hammer price history for coins of similar condition and the interest shown in previous auctions.

Therefore, a reasonable maximum purchase price could be 550 euros.