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

2. Auction History:
- The average hammer price for similar coins in the past has been 83.17 euros.
- The last auction of this coin in 2023 had a hammer price of 45 euros with a condition of 75.
- In previous auctions, hammer prices have varied, but there are examples of sales above 100 euros for coins with similar conditions.

3. Starting Price: The current starting price is 50 euros, which may influence the final price, as hammer prices are usually above the starting price.

4. Price Trends: Observing previous hammer prices, there is a considerable range, but the trend seems to indicate that coins with a condition of 70 can reach hammer prices in the range of 70 to 100 euros, depending on demand at the auction.

Based on these factors, an estimated maximum purchase price for this coin could be between 90 and 110 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate.

Therefore, a reasonable maximum purchase price could be 100 euros.