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 (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 in previous auctions is 83.66 euros.
- Similar coins have been sold in the past with hammer prices that varied, but some examples are:
- 68 euros (2011)
- 80 euros (2012)
- 160.56 euros (2013)
- 170 euros (2015)
- 345 euros (2021, in a condition of 95)
- The trend shows that prices can vary significantly depending on the condition and demand at the time of the auction.

3. Starting Price and Average Starting Price:
- The starting price is 50 euros, and the average starting price is 53.99 euros. This suggests that the hammer price could be above these values, given the auction history.

4. Recent Trends: In the most recent auctions, hammer prices have shown an increase, especially for coins in good condition.

Based on these factors, an estimated maximum purchase price could be in the range of 100 to 120 euros. This is based on the hammer price history for coins of similar condition and the trend of increasing prices in recent auctions.

Therefore, a reasonable maximum purchase price could be 110 euros.