To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Current Condition: The coin has a condition rating of 80 (MS+). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for similar coins has been 359.16 euros.
- In previous auctions, coins with a similar condition (80) have reached hammer prices that varied, but some examples are:
- 240 euros (2019-09-19)
- 300 euros (2019-05-23)
- 260 euros (2019-10-17)
- 280 euros (2020-02-18)
- 360 euros (2022-04-27)
- 550 euros (2023-03-01)

3. Starting Price and Average Starting Price: The current starting price is 300 euros, and the average starting price in the past has been 240.72 euros.

4. Recent Trends: In the most recent auctions, hammer prices have shown an increase, reaching up to 800 euros in a 2022 auction.

Based on this data, an estimated maximum purchase price could be in the range of 400 to 600 euros, considering that the coin is in good condition and that interest in coins of this type seems to be increasing.

Therefore, a reasonable maximum purchase price could be 550 euros.