To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the current condition of the coin.

1. Current Condition: The coin has a condition of 70 (VF-). This indicates that it is in an acceptable state, but not of high quality.

2. Previous Auction Prices: By observing the auction prices of coins with similar conditions (70-75), we can see that:
- In previous auctions, coins with a condition of 70 have reached hammer prices of 150 to 225 euros.
- The last auction with a condition of 70 had a hammer price of 150 euros.

3. Average Hammer Price: The average hammer price for this coin is 258.72 euros, but this includes coins in better conditions.

4. Starting Price: The current starting price is 90 euros, which is relatively low compared to previous hammer prices.

5. Auction Trends: The coin has been auctioned 47 times, of which 44 have sold. This indicates good demand and consistent interest in the coin.

Based on these points, an estimated maximum purchase price could be in the range of 150 to 225 euros, considering that the condition is 70 and the starting price is 90 euros.

Therefore, a reasonable estimated maximum purchase price could be 200 euros. This allows for a margin for competition in the auction, given that the highest previous hammer price for a similar condition was 225 euros.