To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the starting and hammer prices from previous auctions, as well as the coin's condition.

1. Current starting price: 2500 euros.
2. Average starting price in the past: 1415 euros.
3. Average hammer price in the past: 1396 euros.
4. Auction history: The coin has been auctioned 13 times, of which it has sold 10 times. This indicates good demand.
5. Condition: There is no information on the current condition, but in previous auctions, conditions have varied between 10 and 100.

### Analysis of previous prices:
- The auction with the highest hammer price was 4250 euros, although there is no information on the condition.
- The most recent auction with a known hammer price was 440 euros with a condition of 95.
- Hammer prices have varied considerably, suggesting that condition plays an important role in the final price.

### Estimation:
Given that the current starting price is 2500 euros and considering that the average hammer price in the past is 1396 euros, it seems that the starting price is quite high compared to the historical average. However, the good demand (10 out of 13 auctions sold) and the fact that there have been auctions with hammer prices above 4000 euros suggest that there could be significant interest.

If we consider that the starting price is an indicator of the seller's expectation and that the highest hammer price in the past was 4250 euros, an estimated maximum purchase price could be positioned between the starting price and the highest hammer price.

### Estimated maximum purchase price:
Estimation: 4000 euros.

This price reflects a balance between the current starting price and the history of hammer prices, taking into account demand and variability in condition.