Based on the data provided, the coin in question has a grade of 95 (S/C-), with a starting price in the upcoming auction of 18 euros. Additionally, it has been auctioned in the past 86 times, out of which it has been sold 58 times and not sold 28 times.

The average starting price of the coin in previous auctions has been 9.95 euros, while the average final price has been 16.11 euros.

Taking into account the previous prices of the coin in past auctions, where the estimated price has ranged between 6 and 70 euros, and considering that the grade of the coin is high (95), my estimation of the maximum purchase price for this coin in the upcoming auction would be around 65 euros. This is based on the fact that the final price has reached up to 130 euros in the past, so a purchase price of 65 euros could be considered reasonable given the information provided.