Based on the data provided, we can observe that the coin in question has had an average auction closing price of 111.8 euros in previous auctions. Additionally, its condition has been described as '80 (MBC+)'.

Considering that the coin's condition is quite good and the average closing price has been 111.8 euros, we could estimate a maximum purchase price around 120-130 euros. Given that the starting price in this auction is 50 euros, it is likely that the final closing price will be above this value, but it is important to note that the final price may vary depending on demand at the auction.

In summary, an estimated maximum purchase price for this coin in the upcoming auction could be around 120-130 euros.