To estimate a maximum purchase price for the coin in question, let’s consider the following factors:

1. Starting price: 2500 euros.
2. Average hammer price in the past: 3400 euros.
3. Current grade: 100 (MS), which is a very high grade.
4. Historical data: In the previous auction, the same coin with a grade of 95 sold for 3400 euros.

Since the current grade is better (100 versus 95), it is reasonable to assume that the hammer price could be higher than in the previous auction.

Considering that the average hammer price has been 3400 euros and that the grade is better, an estimated maximum purchase price could be in a range between 3400 and 3800 euros.

Therefore, an estimated maximum purchase price could be 3600 euros. This reflects a moderate increase over the previous average hammer price, taking into account the better grade.