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

1. Current starting price: 1200 euros.
2. Coin condition: 95 (S/C-), indicating good preservation.
3. Auction history: The coin has been auctioned once before, with an estimated price of 1500 euros and a hammer price of 600 euros. This suggests that, although the hammer price was low, the estimated price was significantly higher.
4. Average hammer price: 600 euros, which is considerably lower than the current starting price.

Given that the coin's condition is high (95) and considering that the starting price is 1200 euros, which is the same as the average starting price, we can infer that interest in the coin could be high, especially if it has sold well in the past.

However, the previous hammer price was 600 euros, indicating that the market may not be willing to pay much more than that unless there is a change in demand or perception of the coin's value.

Taking all these factors into account, an estimated maximum purchase price could be positioned between the starting price and the previous hammer price. A reasonable range could be:

Estimated maximum purchase price: 900 - 1200 euros.

This allows for some competition in the auction but also considers the hammer price history.