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

1. Starting Price: 900 euros.
2. Condition: 95 (S/C-), indicating that the coin is in very good condition.
3. Auction History: The coin has been auctioned once before, with a hammer price of 900 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, an estimated price of 2000 euros was given, but the hammer price was 900 euros. This indicates that, although the market may have higher expectations, the actual selling price was much lower.

Given that the coin has a sales history at 900 euros and considering that the condition is high, we could estimate that the maximum purchase price could be in a similar or slightly higher range, as condition is an important factor in valuation.

Estimated Maximum Purchase Price: It may be reasonable to consider a maximum purchase price of around 1100 to 1200 euros, taking into account the good condition and potential interest in the coin, but without exceeding the previous hammer price. This would allow for a small premium over the previous hammer price while maintaining a conservative approach given the sales history.