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

1. Current starting price: 350 euros.
2. Condition: The coin has a condition rating of 70 (VF-), indicating that it is in fairly good shape, but not the best possible condition.
3. Auction history: The coin has been auctioned 2 times in the past, and both times it has sold. The average hammer price in the past was 348.5 euros, suggesting that the market is willing to pay close to this price.
4. Average starting and hammer prices in the past: The average starting price was 275 euros and the average hammer price was 348.5 euros. This indicates that interest in the coin is strong, as it has sold for above its starting price.

Given that the current starting price is 350 euros and considering that the average hammer price in the past was 348.5 euros, it is reasonable to think that the hammer price could be in a similar range or slightly higher, especially if there is interest in the auction.

Taking all these factors into account, an estimated maximum purchase price could be between 350 and 400 euros, depending on the competition in the auction and the interest from collectors. However, to be conservative and avoid overpaying, a safe maximum purchase price could be approximately 375 euros.