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+), indicating that it is in relatively good shape. This can positively influence its value.

2. Previous Auction Prices:
- The average hammer price in previous auctions is 132.5 euros.
- In the most recent auction (2022-10-19), the coin was sold for 190 euros with a condition rating of 80.
- In other auctions, the hammer price has varied but has reached up to 220 euros in 2018.

3. Starting Price and Estimates:
- The current starting price is 140 euros, which is slightly higher than the average starting price of 103.25 euros.
- The estimated price for the current auction is 200 euros.

4. Sales Trends: The coin has been sold in 18 of the last 20 auctions, indicating good demand.

Based on these factors, a reasonable maximum purchase price could be in the range of 180 to 220 euros, considering that the condition is good and that it has reached similar prices in previous auctions.

Therefore, an estimated maximum purchase price could be 200 euros. This allows for a margin to compete in the auction without exceeding the market value observed in previous auctions.