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. Average hammer price in the past: 850 euros.
3. Condition of the coin: 95 (S/C-), indicating that it is in very good condition.
4. Estimated price at the previous auction: 1000 euros, although the hammer price was 850 euros.

Given that the coin has a high condition rating (95) and has had a hammer price of 850 euros in the past, it is reasonable to consider that the hammer price could be in a similar range or slightly higher, as the market may have changed since the last auction.

Additionally, the current starting price is 900 euros, suggesting that the seller expects the coin to sell for a higher price.

Taking all these factors into account, an estimated maximum purchase price could be between 900 and 1000 euros. However, to be more conservative and considering the previous average hammer price, a reasonable maximum purchase price could be approximately 950 euros. This allows for some competition in the auction while also staying within a range that reflects the historical value of the coin.