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 of 70 (VF-), indicating that it is in relatively good shape, but not of the highest quality (UNC).

2. Current Starting Price and Previous Prices: The current starting price is 50 euros, and the average starting price in previous auctions is 100.45 euros. This suggests that the current starting price is quite low compared to the historical average.

3. Previous Hammer Prices: The average hammer price in previous auctions is 153.33 euros. This indicates that, in general, buyers are willing to pay more than the starting price.

4. Sales Trends: The coin has been auctioned 10 times, of which it has sold 9 times. This suggests that there is consistent interest in the coin, which may increase its value.

5. Recent Hammer Prices: The hammer prices in recent auctions (for example, 55 euros in 2022) are lower than the average, which could indicate a downward trend in interest or value for the coin.

Given all this, an estimated maximum purchase price could be calculated by considering the average hammer price and adjusting it for the current condition.

If we take the average hammer price of 153.33 euros and adjust it for the condition of 70 (VF-), we could estimate that a reasonable maximum price might be in the range of 100 to 120 euros, given that the condition is not the best.

Therefore, an estimated maximum purchase price could be 120 euros.