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

1. Current starting price: 400 euros.
2. Average hammer price in the past: 565 euros.
3. Hammer price history:
- 2020: 120 euros (grade 30)
- 2016: 950 euros (grade unknown)
- 2016: 180 euros (grade unknown)
- 2015: 300 euros (grade unknown)
- 2014: 240 euros (grade unknown)
- 2018: 100 euros (grade 30)
- 2017: 200 euros (grade unknown)
- 2024: 460 euros (grade 70)
- 2024: 1500 euros (grade 95)

4. Price analysis:
- Hammer prices vary significantly, ranging from 100 euros to 1500 euros, depending on the grade and other factors.
- The general trend shows that coins in better condition tend to reach higher prices.
- The last auction with a grade of 70 reached 460 euros, suggesting there is significant interest in medium-quality coins.

5. Maximum price estimation:
- Since there is no information about the condition of the current coin, but considering that the starting price is 400 euros and the average hammer price is 565 euros, a reasonable maximum purchase price could be in the range of 600 to 700 euros, assuming the coin has an acceptable condition.

Therefore, an estimated maximum purchase price for this coin could be 650 euros. This is based on the analysis of previous hammer prices and the market context.