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 previous auctions: 1648 euros.
3. Average hammer price in previous auctions: 1900.65 euros.
4. Hammer price history: Hammer prices have varied, with some reaching up to 3300 euros in previous auctions, although most have sold in a lower range.

Since there is no information about the condition of the current coin, it is difficult to make a direct comparison. However, we can observe that:

- Most coins with higher conditions (above 80) have had hammer prices ranging between 1500 and 2500 euros, with some exceptional cases reaching higher prices.
- The last auction with a hammer price of 4700 euros was conducted with a condition of 100, indicating that the quality of the coin has a significant impact on the price.

Taking these factors into account, an estimated maximum purchase price could be set in a range between the average hammer price (1900.65 euros) and the highest observed price (3300 euros), depending on demand and the quality of the coin.

Estimated maximum purchase price: 2500 euros.

This price reflects a balance between the price history and the uncertainty regarding the current condition of the coin.