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

1. Starting price: 1200 euros.
2. Average hammer price in the past: 1300 euros.
3. Condition of the coin: 100 (Uncirculated), indicating it is in excellent condition.
4. Auction history: It has been auctioned once before, with a hammer price of 1300 euros.

Given that the coin is in high condition and has reached a hammer price of 1300 euros in the past, it is reasonable to assume that interest in this coin will remain. Additionally, the fact that there have been no failed sale attempts suggests that there is demand.

Taking these factors into account, an estimated maximum purchase price could be slightly above the previous average hammer price, considering that the market may have evolved.

Therefore, an estimated maximum purchase price could be approximately 1400 euros. This reflects a slight increase over the previous hammer price, taking into account the good condition and potential demand.