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

1. Current starting price: 700 euros.
2. Coin condition: 80 (MBC+), indicating good preservation.
3. Auction history:
- In 2020, it was auctioned with a starting price of 500 euros and sold for 800 euros.
- In 2019, the starting price was 460 euros and it sold for 585 euros.
- In 2016, the starting price was 500 euros and it sold for 500 euros (no increase).
- In 2014, the starting price was 1200 euros and it sold for 1550 euros, indicating high interest in that auction.
- In 2023, the starting price was 700 euros and it sold for 925 euros.

4. Average hammer price: 872 euros, suggesting that, in general, coins of this reference tend to sell above their starting price.

Given that the coin is in good condition (80) and considering the hammer price history, an estimated maximum purchase price could be slightly higher than the average hammer price.

Estimation:
- Based on the average hammer price (872 euros) and the fact that it has reached higher prices in previous auctions, a reasonable maximum purchase price could be in the range of 900 to 950 euros.

Therefore, I would recommend considering a maximum purchase price of 950 euros for this coin at the auction.