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

1. Starting price: 60 euros.
2. Current condition: 50 (fine), indicating average quality.
3. Auction history:
- In 2020, it sold for 95 euros with a condition of 30.
- In 2020, it sold for 65 euros with a condition of 70.
- In 2016, it sold for 75 euros (no condition information).
- In 2022, it sold for 80 euros with a condition of 30.

4. Average hammer price: 78.75 euros, indicating that, in general, coins of this reference tend to sell above the starting price.

5. Price trends: We observe that coins in better condition have reached higher prices. The condition of 70 reached a hammer price of 65 euros, while the condition of 30 had hammer prices of 95 and 80 euros.

Given that the condition of the coin at auction is 50, which is intermediate, and considering the average hammer price of 78.75 euros, we can estimate that the maximum purchase price could be in a range above the starting price, but not as high as the hammer prices of the higher conditions.

Estimated maximum purchase price: It may be reasonable to set a maximum purchase price around 85-90 euros, as this aligns with the price history and current condition. This allows for a margin for competition in the auction, considering that the starting price is 60 euros.