To estimate a maximum purchase price for the coin with a grade of 95 (S/C-), we can analyze the historical data from previous auctions of coins with the same grade and similar characteristics.

1. Data from previous auctions:
- In the past, coins with a grade of 95 have had hammer prices that varied, but there are several examples where the hammer price has reached up to 70 euros (as in the auction on 2018-10-17).
- The average hammer prices for coins with a grade of 95 seem to be in a range of 20 to 35 euros, with some higher peaks.

2. Starting price and estimates:
- The current starting price is 18 euros, and the average hammer price in the past has been 27.32 euros.
- Given that the coin's grade is high (95), it is reasonable to expect that the hammer price will be above the historical average.

3. Final estimation:
- Considering the grade, the starting price, and previous hammer prices, an estimated maximum purchase price could be between 40 and 60 euros. This is based on the behavior of previous auctions and the interest that a coin in such good condition may generate.

Therefore, an estimated maximum purchase price for this coin could be 50 euros.