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 12 times and has sold on all occasions.
- The average hammer price in previous auctions is 258.67 euros.
- The hammer prices in previous auctions for coins with similar conditions (70 and 75) have ranged between 200 and 330 euros.

3. Starting Price: The current starting price is 200 euros, which is a reasonable starting point.

4. Price Trends: Observing previous hammer prices, it seems that coins with a condition of 70 have reached hammer prices of up to 280 euros in the past.

5. Data-Based Estimation: Given that the average hammer price is 258.67 euros and considering that the condition of the coin is 70, an estimated maximum purchase price could be in the range of 280 to 300 euros, taking into account that the market can fluctuate and that demand may influence the final price.

Therefore, an estimated maximum purchase price for this coin could be 300 euros.