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

1. Current Condition: The coin has a condition of 30 (BC+), which indicates that it is in a relatively low state compared to other coins that have been auctioned. This will negatively affect its value.

2. Auction History: The coin has been auctioned 52 times, with an average hammer price of 290.14 euros. However, hammer prices vary significantly depending on the condition of the coin.

3. Previous Prices: By observing the hammer prices of coins with similar conditions, we can see that prices have fluctuated. For example, in previous auctions, coins with conditions ranging from 30 to 70 have had hammer prices ranging from 80 to 200 euros.

4. Recent Trends: In the most recent auctions, hammer prices for coins with higher conditions have been higher, but given that the condition of this coin is low, it is reasonable to expect a lower hammer price.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 80 to 150 euros. This is based on the analysis of previous hammer prices for coins with similar conditions and the current market context.

Therefore, a reasonable maximum purchase price could be 120 euros.