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

1. Current Condition: The coin has a condition of 70 (MS-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price in previous auctions is 411.15 euros, indicating that, in general, coins of this reference tend to sell for relatively high prices.
- The last auction of this coin (2024-09-19) had a hammer price of 240 euros with a condition of 70, suggesting that this is a reasonable price for a coin in similar conditions.

3. Starting Price and Previous Prices:
- The current starting price is 90 euros, which is quite low compared to the average hammer price.
- In previous auctions, hammer prices have varied, but there are examples of sales exceeding 400 euros, especially for coins in better condition.

4. Sales Trends: The coin has been sold in 13 out of 15 auctions, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 240 to 350 euros, considering that the condition is a limiting factor and that the average hammer price is significantly higher.

Therefore, a reasonable maximum purchase price could be 350 euros.