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-), indicating an acceptable but not excellent state. This may influence the price, as coins in better condition typically fetch higher prices.

2. Starting Price and Previous Prices: The current starting price is 90 euros. In previous auctions, the average hammer price has been 139.48 euros, suggesting that buyers are willing to pay significantly more than the starting price.

3. Sales History: The coin has been auctioned 35 times, of which it has sold 33 times. This indicates good demand and a history of successful sales.

4. Previous Hammer Prices: Looking at previous hammer prices for coins with a similar condition (70), the highest recorded price was 240 euros, while other hammer prices in the 70 condition range have been between 59 and 220 euros.

5. Recent Trends: In the most recent auctions, hammer prices have shown a trend of being higher, which could indicate an increase in demand or in the coin's value.

Based on these factors, an estimated maximum purchase price could be in the range of 180 to 240 euros, considering that the average hammer price has been 139.48 euros and there are precedents of higher hammer prices in the past.

Therefore, a reasonable maximum purchase price could be 200 euros. This allows for a margin for competition in the auction, given the price history and the condition of the coin.