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

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

2. Auction History:
- The average hammer price for similar coins in condition 70 has been 35 euros (based on auctions from 2019 and 2020).
- In previous auctions, the hammer price has varied, but it has reached up to 80 euros for coins in better condition (condition 85).

3. Starting Price and Average Hammer Price:
- The current starting price is 30 euros, and the average hammer price in the past has been 42.28 euros.

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

Based on these factors, an estimated maximum purchase price could be between 50 and 70 euros, considering that the condition is good and that the price history shows that similar coins have reached higher prices in the past.

Therefore, a reasonable maximum purchase price could be 65 euros.