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

1. Coin Condition: The coin to be auctioned has a condition rating of 100 (S/C), indicating that it is in excellent condition. This generally increases its value compared to coins with lower conditions.

2. Auction History:
- The average hammer price in previous auctions is 27 euros.
- The coin has been auctioned 14 times, of which it has sold 9 times, indicating good demand.
- Previous hammer prices varied, but there are examples of auctions reaching up to 110 euros under similar conditions.

3. Starting Price and Estimated Prices:
- The current starting price is 6 euros, which is relatively low compared to the average hammer price.
- The average starting price in previous auctions is 17.62 euros, suggesting that the current starting price could be a good opportunity.

4. Recent Trends: In the most recent auctions, estimated prices have been higher, suggesting that interest in this coin may be increasing.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 50 to 70 euros, considering that the condition is excellent and there is a history of hammer prices that supports this estimate.