To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the conditions of the auctioned coins.

1. Starting price: 200 euros.
2. Average hammer price: 278.35 euros.
3. Previous hammer prices:
- Similar coins with conditions ranging from 80 to 95 have sold for prices varying from 51 euros to 1400 euros.
- The most recent auction had a hammer price of 650 euros and a condition of 85.
- The 2022 auction had a hammer price of 400 euros and a condition of 95.

4. Condition: No specific information is provided about the condition of the current coin, making the estimation more complicated. However, we can observe that coins with higher conditions tend to reach significantly higher hammer prices.

5. Trends:
- Coins with conditions from 80 to 95 have had hammer prices ranging from 130 to 1400 euros.
- The general trend shows that the hammer price can be considerably higher than the starting price.

Given that there is no information about the condition of the current coin, but considering that the starting price is 200 euros and the average hammer price is 278.35 euros, an estimated maximum purchase price could be set at a higher range, considering previous auctions.

Estimated maximum purchase price: Based on the data, a reasonable maximum purchase price could be between 400 to 500 euros, as this range has been reached in previous auctions with similar conditions. However, if the condition is high, the price could be even higher.