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

1. Coin Condition: The coin has a condition rating of 100 (S/C), indicating that it is in very good condition. This generally translates to a higher price compared to coins with lower condition ratings.

2. Current and Previous Prices: The current starting price is 150 euros. In previous auctions, we have seen hammer prices that varied significantly, but there are examples of similar coins that have reached hammer prices of up to 700 euros (in the case of a coin with a condition rating of 110).

3. Price Trends: The average hammer price for similar coins is 104.51 euros, but there are examples of much higher hammer prices, especially for coins in conditions similar to the current one.

4. Supply and Demand: The coin has been auctioned 60 times in the past, with a sell-through rate of 91.67% (55 out of 60). This suggests that there is consistent interest in this coin.

5. Recent Hammer Prices: In the most recent auction, a similar coin was sold for 312 euros, indicating that there is potential for higher prices in the future.

Taking all these factors into account, an estimated maximum purchase price for this coin could be in the range of 300 to 400 euros, given its condition and the price trends in previous auctions. However, it is important to remember that the final price may vary depending on the competition in the auction and the demand at the time of sale.