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

1. Current Condition: The coin has a grade of 70 (MS-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for coins with similar grades (70) in the past has been approximately 240-360 euros.
- The last auction of a coin with a grade of 70 had a hammer price of 320 euros.
- Overall, hammer prices for grade 70 coins have ranged between 200 and 360 euros in previous auctions.

3. Starting Price and Average Hammer Price:
- The current starting price is 300 euros, which is slightly higher than the average starting price of 248 euros.
- The average hammer price is 333.03 euros, suggesting that the coin could sell for a price close to this value.

4. Recent Trends:
- In the most recent auctions, hammer prices have shown a trend of being higher, especially for coins in good condition.

Based on these factors, an estimated maximum purchase price for this coin could be around 360 euros, considering that the condition is acceptable and the auction history shows hammer prices in that range. However, since the starting price is 300 euros, buyers may be willing to pay a little more, but not much beyond 360 euros, unless there is significant interest in the coin.