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

1. Current Condition: The coin has a condition of 70 (MS-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Previous Prices: By observing previous auction prices for coins with similar conditions, we can see that prices have varied. For example, in past auctions, coins with conditions ranging from 70 to 80 have reached hammer prices between 120 and 210 euros.

3. Starting Price and Average Hammer Price: The current starting price is 175 euros, and the average hammer price in the past has been 147.83 euros. This suggests that the starting price is relatively high, but not unusual for a coin of this condition.

4. Recent Trends: In the most recent auctions, hammer prices for coins of similar condition have shown an increase, reaching up to 230 euros in some cases.

Based on these factors, an estimated maximum purchase price could be around 210-230 euros, considering that interest in coins of this condition may be high and that the starting price is reasonable compared to previous hammer prices.

Therefore, a reasonable maximum purchase price could be 230 euros.