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 70 (MS-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price in previous auctions is 287 euros.
- The coin has been auctioned 29 times, of which it has sold 26 times, indicating good demand.
- In recent auctions, hammer prices have varied, but there are examples of sales exceeding 200 euros.

3. Starting Prices and Estimates:
- The current starting price is 150 euros, which is reasonable given the history of starting and hammer prices.
- The estimated price for this auction is 150 euros, suggesting that auctioneers expect moderate interest.

4. Comparison with Previous Prices:
- In previous auctions, coins with similar conditions have reached hammer prices ranging from 90 to 600 euros, depending on the condition and demand at that time.

5. Recent Trends:
- In the most recent auctions, hammer prices have shown an increase, which could indicate a rising trend in interest for this coin.

Based on these factors, an estimated maximum purchase price could be around 300 euros. This is based on the history of hammer prices and the current condition of the coin, as well as the price trend in recent auctions. However, it is important to note that the final price may vary depending on competition in the auction and the interest of other buyers.