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

1. Current Condition: The coin has a condition of 70 (VF-), indicating that it is in an acceptable state, but not of high quality. This generally affects the price, as coins in better condition tend to fetch higher prices.

2. Current Starting Price and Previous Prices: The current starting price is 90 euros, and the average starting price in previous auctions is 121.33 euros. This suggests that the current starting price is relatively low compared to the historical average.

3. Previous Hammer Prices: The average hammer price in previous auctions is 154 euros. This indicates that, generally, coins of this reference tend to sell for a price higher than the starting price.

4. Sales Trends: The coin has been auctioned 7 times, of which it has sold 5 times. This suggests that there is consistent interest in this coin, which may influence its price.

5. Comparison with Previous Prices: In the most recent auction (2023), a coin in condition 95 sold for 520 euros. This indicates that there is a market for high prices, but also that condition is a critical factor.

Given all this, an estimated maximum purchase price could be set in a range between the average hammer price (154 euros) and a bit more, considering that the condition is lower than that of the last successful auction.

Therefore, a reasonable maximum purchase price could be around 150-180 euros. This allows for a margin for competition in the auction, but also takes into account the condition of the coin.