Given that the coin has a grade of 50 (fine) and there are no historical data from previous auctions, it is difficult to establish a maximum estimated purchase price based on prior experience. However, we can consider some factors:

1. Starting Price: The starting price is 60 euros, which indicates the minimum value expected to be obtained at the auction.
2. Condition: A grade of 50 (fine) suggests that the coin is in an acceptable state, but it is not of high quality. This may limit collectors' interest and, therefore, the price.
3. No Previous Sales: The lack of previous sales may indicate that there is no established market for this particular coin, which could make bidders more cautious.

Given these factors, a maximum estimated purchase price could be slightly higher than the starting price, but not by much, as the condition is not high and there is no sales history to support a higher price.

Therefore, a maximum estimated purchase price could be in the range of 70 to 80 euros. This would allow bidders to have a margin to compete, but it also reflects the uncertainty given the lack of historical data.