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

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

2. Auction History: By observing previous hammer prices for coins with a similar condition (95), we can see that the hammer prices have varied. For example:
- In recent auctions, hammer prices for coins with a condition of 95 have ranged from 25 to 45 euros.
- In earlier auctions, the highest hammer price for a coin with a condition of 95 was 85 euros.

3. Average Hammer Price: The average hammer price for this coin is 20.91 euros, but given the high condition, we can expect the actual hammer price to be above this average.

4. Auction Trends: The coin has been auctioned 85 times, of which 73 have been successful sales. This indicates a consistent interest in the coin, which may increase its value.

5. Starting Prices and Estimates: The current starting price is 12 euros, and the average starting price is 13.35 euros. However, given the hammer price history and the condition, it is reasonable to expect the hammer price to be above these values.

Based on these factors, an estimated maximum purchase price for this coin could be between 45 and 70 euros. This is based on the hammer price history for coins of similar condition and the demonstrated interest in previous auctions.