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

1. Condition: The coin has a condition rating of 80 (MS+), indicating that it is in fairly good shape, but not the best possible condition. This can influence the price, as coins in better condition tend to fetch higher prices.

2. Current listing price and previous prices: The current listing price is 1550 euros. In previous auctions, we have seen hammer prices that vary, but generally, hammer prices for coins with similar conditions have been in the range of 1300 to 1700 euros, with some exceptional cases reaching up to 1800 euros.

3. Price trends: Looking at the hammer prices from previous auctions, it seems there is a trend for coins of similar condition to sell in a range of 1500 to 1700 euros, with some spikes in recent auctions.

4. Average hammer price: The average hammer price for this coin in the past has been approximately 1365.75 euros, suggesting that the hammer price may be around this value, but since the current listing price is higher, it is reasonable to expect that the hammer price will also be higher.

Based on these factors, an estimated maximum purchase price for this coin could be between 1700 and 1800 euros, considering that interest in the coin may have increased and that the condition is quite good. However, it is important to keep in mind that the final price will depend on the competition in the auction and the interest of collectors at that time.

Therefore, a reasonable maximum purchase price could be 1800 euros.