To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

1. Coin Condition: The coin has a condition rating of 95 (S/C-), indicating that it is in very good shape. This generally increases its value compared to coins with lower conditions.

2. Auction History:
- The average hammer price for similar coins in the past is 67.89 euros.
- The coin has been auctioned 24 times, of which it has sold 19 times, indicating good demand.
- Previous hammer prices for coins with a similar condition (95) have varied, but there are examples of auctions reaching up to 50 euros in recent sales.

3. Starting Price and Estimates:
- The current starting price is 12 euros, which is relatively low compared to the average hammer price.
- The estimated hammer price in previous auctions for coins with a condition of 95 has reached up to 30 euros or more.

Considering these factors, an estimated maximum purchase price could be in the range of 50 to 70 euros, given that the condition is high and there is a history of hammer prices supporting this estimate. However, since the starting price is 12 euros, buyers may be willing to bid more, especially if there is interest in the coin.

Therefore, a reasonable maximum purchase price could be between 60 and 70 euros.