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 fairly good shape, but not the best possible condition.

2. Auction History:
- The average hammer price for similar coins has been 1136.93 euros.
- In previous auctions, coins with a similar condition (80) have reached hammer prices that vary, but some examples are:
- 700 euros (2021-03-18)
- 900 euros (2021-02-18)
- 950 euros (2023-02-16)
- 900 euros (2023-03-16)
- The trend shows that, although there are variations, the hammer prices for similar conditions have been in a range of 700 to 950 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 500 euros, which is below the average starting price of 632.35 euros. This suggests that there is potential for the hammer price to be higher.

4. Demand and Supply: Since there are no auctions scheduled in the coming days, this could increase competition among bidders, which could drive up the hammer price.

Based on these factors, an estimated maximum purchase price could be in the range of 900 to 1200 euros, considering that the average hammer price has been 1136.93 euros and that the condition of the coin is good.

Therefore, a reasonable maximum purchase price could be approximately 1100 euros. This allows for some margin for competition in the auction, while also staying within the limits of what has been seen in the past for coins of similar condition.