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

1. Current Condition: The coin has a condition rating of 90 (EF), which indicates that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price for similar coins is 155.35 euros.
- In previous auctions, we have seen hammer prices that varied considerably, but some relevant examples are:
- A coin with a condition of 90 sold for 295 euros in 2019.
- Another with a condition of 85 sold for 220 euros in 2018.
- The last auction of a similar coin with a condition of 80 had a hammer price of 200 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 110 euros, and the average starting price in the past has been 92.27 euros.

4. Sales Trends: Out of the 48 times it has been auctioned, 44 have been sold, indicating good demand.

Based on this data, an estimated maximum purchase price could be in the range of 250 to 300 euros, considering that the condition is good and there are precedents for sales in that range for coins of similar condition.

Therefore, a reasonable maximum purchase price could be approximately 280 euros.