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

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

2. Previous Auction Prices:
- The coin has been auctioned 9 times and has sold on all occasions.
- The average hammer price in previous auctions is 1661.11 euros.
- The hammer prices in previous auctions varied, but there are examples of hammer prices of 1400 euros (condition 80) and 1800 euros (condition 95).

3. Current Starting Price: The starting price is 1450 euros, which is slightly lower than the previous average hammer price.

4. Price Trends: Observing the previous hammer prices, it seems that coins with a similar condition (70) have reached hammer prices of up to 1800 euros in the past.

5. Data-Based Estimation: Given that the condition of the coin is 70 and considering that there have been successful sales in the range of 1400 to 1800 euros, an estimated maximum purchase price could be positioned in the upper range of these prices.

Taking all these factors into account, an estimated maximum purchase price for this coin could be approximately 1800 euros. This is based on the history of hammer prices and the current condition of the coin.