To estimate a maximum purchase price for the coin in question, we will consider several factors based on the provided data:

1. Current starting price: 800 euros.
2. Auction history: The coin has been auctioned 10 times, of which it has sold 8 times. This indicates good demand.
3. Previous prices:
- The average hammer price in previous auctions is 1096.88 euros.
- The hammer prices in previous auctions varied, but there are examples of sales at 1200 euros (2020) and 1400 euros (2016).
4. Condition: There is no specific information about the condition of the current coin, but in previous auctions, the conditions have ranged between 70 and 85, suggesting that the coin could be in an acceptable state.

Given that the average hammer price is approximately 1096.88 euros and considering that the starting price is 800 euros, an estimated maximum purchase price could be set in a range between the average hammer price and a bit more, given that the coin has a history of successful sales.

Estimated maximum purchase price: It could be reasonable to estimate a maximum purchase price of around 1200 euros, taking into account the auction history and the demand observed in previous auctions.