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 increases its value compared to coins with lower conditions.

2. Auction History:
- The average hammer price for this coin in the past has been 42.18 euros.
- In previous auctions, we have seen hammer prices that varied significantly, ranging from 5 euros to 220 euros, depending on the condition and other factors.

3. Starting Prices and Estimates:
- The current starting price is 12 euros, which is relatively low compared to the average hammer price.
- The estimated price for this auction is 20 euros, which is also below the average hammer price.

4. Price Trends:
- In recent auctions, the hammer price has been around 42 euros, suggesting that there is sustained interest in this coin.

Given all this, an estimated maximum purchase price could be around 60-80 euros, considering that the condition is high and that interest in the coin appears to be strong. This also takes into account that in previous auctions, higher hammer prices have been reached, especially for coins of similar condition.