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

1. Current Condition: The coin has a condition rating of 80 (MBC+), indicating 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 in the past is 149.18 euros.
- The condition of the coins auctioned in the past varied, but there are examples of coins with a condition of 80 that have sold for prices around 150 euros.

3. Previous Hammer Prices:
- In previous auctions, coins with a condition of 80 have reached hammer prices of up to 240 euros (as seen in the auction on 2021-10-20).
- There are also examples of coins with a condition of 70 that sold for 110 euros and 150 euros.

4. Starting Price and Estimated Price:
- The current starting price is 110 euros, and the estimated price is 150 euros. This suggests that the seller expects the coin to sell for a price higher than the starting price.

5. Market Trends: Given that the coin has been auctioned 21 times and has had a high sales percentage (19 out of 21), this indicates a consistent interest in this coin, which may influence the price.

Based on these factors, an estimated maximum purchase price could be in the range of 180 to 240 euros, considering that the condition is good and there are precedents for successful sales in that range. However, to be more conservative and avoid overpaying, a reasonable maximum purchase price could be approximately 200 euros.