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 (MS-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Previous Prices: By looking at previous auction prices for coins with similar conditions (70 and 75), we can see that:
- In 2020, a coin with a condition of 70 was auctioned for 43 euros.
- In 2018, another coin with a condition of 70 was auctioned for 50 euros.
- In 2022, a coin with a condition of 70 was auctioned for 75 euros.

3. Price Trends: The average auction price for similar coins is 175.17 euros, but this includes coins in better condition. Given that the condition of this coin is 70, it is reasonable to expect that its auction price will be below this average.

4. Starting Price: The starting price is 25 euros, indicating that the auction house expects moderate interest in the coin.

5. Sales History: The coin has been auctioned 47 times, of which 45 have sold. This suggests that there is an active market for this coin.

Based on these factors, an estimated maximum purchase price for this coin could be between 50 and 80 euros, considering that the condition is a limiting factor and that previous auction prices for coins of similar condition have been in that range.

Therefore, a reasonable maximum purchase price could be 70 euros.