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

1. Starting price: 90 euros.
2. Average hammer price in the past: 140 euros. This indicates that, in general, coins of this reference tend to sell for a price higher than the starting price.
3. Condition: The coin has a condition of 70 (VF-), which suggests that it is in relatively good shape, although it is not of the highest quality (UNC).
4. Auction history: It has been auctioned once and sold on that occasion, indicating that there is interest in the coin.

Given that the average hammer price is significantly higher than the starting price, and considering the condition of the coin, an estimated maximum purchase price could be positioned between the average hammer price and a little more, since the condition is good but not excellent.

Therefore, an estimated maximum purchase price could be around 160-180 euros. This is based on the interest that the coin may generate and its state of preservation.