To estimate a maximum purchase price for the coin in question, we can analyze the provided data:

1. Current starting price: 1500 euros.
2. Average starting price in the past: 1700 euros.
3. Average hammer price in the past: 2300 euros.
4. Condition of the coin: 95 (S/C-), which is a high condition.
5. Auction history:
- In 2015, it started at 1800 euros and was hammered at 2100 euros.
- In 2014, it started at 2000 euros and was hammered at 2100 euros (condition 95).
- In 2021, it was hammered at 3000 euros (condition 95).
- In 2023, it started at 1500 euros and was hammered at 2000 euros.

Given that the coin has a high condition (95) and has a history of hammer prices exceeding the current starting price, we can consider that the hammer price could be in a higher range.

### Analysis:
- The average hammer price (2300 euros) and previous hammer prices (2100 and 3000 euros) suggest that there is significant interest in this coin.
- The last auction in 2023 had a hammer price of 2000 euros, indicating that interest remains.

### Estimation:
Taking all these factors into account, an estimated maximum purchase price could be between 2300 and 2500 euros, as this price reflects both market interest and the condition of the coin.

Estimated maximum purchase price: 2500 euros.