To estimate a maximum purchase price for the coin in question, we will consider several factors:

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. Auction History:
- The average hammer price for coins of similar condition (around 70) has been approximately 15 to 20 euros in recent auctions.
- In the past, coins with a condition of 70 have reached hammer prices of up to 45 euros (as seen in the auction on 2020-10-21).

3. Starting Price and Average Starting Price:
- The current starting price is 12 euros, which is relatively low compared to the average hammer price of 32.94 euros.
- The average starting price of 17.98 euros also suggests that there is potential for an increase in the hammer price.

4. Recent Trends:
- In the most recent auctions, the hammer price has ranged between 15 and 30 euros for coins of similar condition.

Based on these factors, an estimated maximum purchase price for this coin could be between 25 and 35 euros. This is based on the historical hammer prices for coins of similar condition and the potential for an increase in the hammer price in the current auction.

Therefore, a reasonable maximum purchase price could be 30 euros.