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

1. Current starting price: 900 euros.
2. Average starting price in previous auctions: 928.57 euros.
3. Average hammer price in previous auctions: 1463.5 euros.
4. Auction history: The coin has been auctioned 10 times and has sold in all of them, indicating good demand.

### Analysis of previous prices:
- In the auctions of 2020 and 2018, the hammer prices were 1500 and 1460 euros, respectively, with starting prices of 800 and 1200 euros.
- In other auctions, hammer prices have ranged between 850 and 1900 euros, depending on the condition and starting price.

### Considerations:
- The condition of the current coin is not specified, which may influence its value. However, previous hammer prices for coins of similar condition (95) have been consistently high.
- Given that the starting price is 900 euros and the average hammer price is 1463.5 euros, there is considerable room for a higher hammer price.

### Estimation of the maximum purchase price:
Based on the history of hammer prices and the average hammer price, a reasonable maximum purchase price could be a percentage of the average hammer price. Considering that the starting price is 900 euros, a maximum purchase price could be between 80% and 90% of the average hammer price.

Calculating:
- 80% of 1463.5 euros = 1170.8 euros
- 90% of 1463.5 euros = 1316.15 euros

### Conclusion:
An estimated maximum purchase price for the coin could be between 1170 and 1316 euros, depending on the demand at the auction and the final condition of the coin.