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-), indicating that it is in an acceptable state, but not of high quality. This may influence its value compared to coins in better condition.

2. Auction History:
- The average hammer price of similar coins in the past is 113.86 euros.
- In previous auctions, hammer prices have varied significantly, ranging from 26 euros to 260 euros, depending on the condition and other factors.

3. Starting Price: The current starting price is 15 euros, suggesting that the coin is expected to sell for a lower price compared to its historical value.

4. Sales Trends: Since this coin has sold every time it has been auctioned, this indicates a steady demand.

5. Comparison with Previous Prices:
- In previous auctions with similar condition (70), hammer prices have been 26 euros and 55 euros, suggesting that the price range could be between 26 and 55 euros for a coin in VF- condition.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 50 to 70 euros, considering that the average hammer price of similar coins is 113.86 euros, but adjusted for the current condition and starting price.

Therefore, a reasonable estimated maximum purchase price could be 60 euros.