Based on the provided data, we can conduct an analysis to estimate a maximum purchase price for the coin in question.

1. Starting price: 600 euros.
2. Condition: 85 (ebc-), indicating good condition, although not the best possible.
3. Auction history: The coin has been auctioned once before, with a hammer price of 600 euros, which matches the current starting price. This suggests that the market has valued this coin in that range.
4. Previous estimated price: In the previous auction, a price of 1000 euros was estimated, but the hammer price was 600 euros, indicating that the actual interest from buyers was lower than the estimate.

Given that the coin has a sales history at 600 euros and considering that the condition is good but not exceptional, a maximum purchase price could be in the range of 600 to 800 euros. This is because, although the previous hammer price was 600 euros, interest may have increased slightly, but not enough to reach the estimated price of 1000 euros.

Therefore, an estimated maximum purchase price could be 800 euros.