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 (VF-). This indicates that it is in an acceptable state, but not among the best qualities.

2. Auction History:
- The average hammer price for coins of similar condition (70) in the past has been approximately 51 euros (based on auctions from 2018 and 2023).
- Coins with higher conditions (85 and 95) have reached hammer prices of up to 420 euros, but that does not directly apply to this coin.

3. Starting Price and Average Hammer Price:
- The current starting price is 18 euros, which is quite low compared to the average hammer price of 100.41 euros.
- The average starting price of 62.21 euros also suggests that there is potential for an increase in the hammer price.

4. Sales Trends: The coin has been sold in 38 out of 42 auctions, indicating good demand.

5. Comparison with Previous Prices:
- In previous auctions, coins with a condition of 70 have had hammer prices that vary, but they have generally sold for above 30 euros.

Based on these factors, an estimated maximum purchase price for this coin could be between 50 and 70 euros, considering that the condition is a limiting factor and that the average hammer price for similar conditions has been around 51 euros.

Therefore, a reasonable maximum purchase price could be 70 euros.