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

1. Current Condition: The coin has a condition rating of 70 (VF-), indicating that it is in acceptable shape, but not in the best condition. This may influence 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 198.85 euros. The average hammer price is 230.09 euros, suggesting that, in general, coins of this reference tend to sell for above their starting price.

3. Auction History: The coin has been auctioned 13 times, of which it has sold 11 times. This indicates good demand. Additionally, the highest recorded hammer price was 550 euros in 2017, although this may not be representative due to a lack of information about the condition of that coin.

4. Price Trends: Observing the hammer prices from previous auctions, we can see considerable variability. For example, in 2020, the coin sold for 95 euros, while in 2018 it sold for 130 euros. This suggests that the price may fluctuate depending on demand at the time of the auction.

5. Data-Based Estimation: Given that the average hammer price is 230.09 euros and considering that the condition of this coin is 70, an estimated maximum purchase price could be positioned between the average hammer price and a bit lower, given its state.

Taking all these factors into account, an estimated maximum purchase price for this coin could be approximately 200-220 euros. This is based on the price history and current condition, suggesting that it could reach a reasonable price at auction.