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

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. Previous Prices: Looking at previous auction prices, we can see that the coin has reached auction prices of up to 600 euros in similar conditions (condition rating 85) and 480 euros in higher condition (85).

3. Average Auction Price: The average auction price for this coin is 381.45 euros, which gives us a good reference for what buyers are willing to pay.

4. Starting Price: The current starting price is 350 euros, indicating that the seller has reasonable expectations for an auction price.

5. Auction Trends: The coin has been auctioned 13 times, with a high sales percentage (12 out of 13). This suggests that there is consistent interest in the coin.

Given all this, and considering that the condition of the coin is slightly lower than those that have reached higher prices, an estimated maximum purchase price could be in the range of 400 to 500 euros. This is based on the fact that, although the condition is not the best, the interest in the coin and previous auction prices suggest it could reach a competitive price.

Therefore, an estimated maximum purchase price could be 450 euros.