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 rating of 70 (VF-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for similar coins in the past is 95.9 euros.
- The condition of the coins auctioned in the past varies, but there are examples of coins with a condition of 80 that sold for 70 euros and others with a condition of 95 that reached up to 150 euros.

3. Starting and Hammer Prices:
- The current starting price is 20 euros, indicating that there is considerable room for the hammer price to be higher.
- In previous auctions, hammer prices have varied, but there are examples where coins with similar conditions have reached hammer prices of up to 150 euros.

4. Sales Trends:
- Out of the 14 times this coin has been auctioned, it has sold 12 times, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 100 to 120 euros, considering that the coin's condition is 70 and that there are examples of higher hammer prices in the past. This also takes into account the average hammer price of 95.9 euros and the potential for the coin to attract interested collectors.

Therefore, an estimated maximum purchase price could be 110 euros.