To estimate a maximum purchase price for the coin that is going to be auctioned, we can consider several factors based on the provided data:

1. Starting price: 600 euros.
2. Auction history: The coin has been auctioned 80 times, of which it has sold 67 times. This indicates a good sales rate (83.75%).
3. Previous prices:
- The average hammer price is 195.83 euros.
- The average starting price is 105.28 euros.
- There have been recorded hammer prices that vary significantly, with some reaching up to 1600 euros in the past (such as in the 2014 auction).

4. Condition: There is no information about the condition of this coin, which may affect its value. However, in the history, there are coins with conditions ranging from 80 to 95 that have reached high hammer prices.

5. Price trends: In previous auctions, hammer prices have varied significantly, and some have exceeded the current starting price.

Given that the starting price is 600 euros and considering the history of hammer prices, an estimated maximum purchase price could be slightly higher than the starting price, but not excessively high due to the lack of information about the condition.

Estimated maximum purchase price: 800 euros.

This price reflects a balance between the starting price and the potential hammer price based on the history, taking into account the uncertainty regarding the condition.