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

1. Current Condition: The coin has a condition of 25 (BC), which is quite low. This will negatively affect its value compared to coins in better condition.

2. Auction History:
- The average hammer price for similar coins in better condition (75-80) has been approximately 98.26 euros.
- Previous auctions show that coins with higher conditions have reached hammer prices ranging from 50 to 230 euros, depending on the condition.

3. Starting Price: The starting price is 30 euros, indicating that the seller has moderate expectations.

4. Sales Trends: Out of the 23 times it has been auctioned, 19 have been sold, indicating good demand, although the condition of this coin is a limiting factor.

Given that the condition of this coin is low (25), and considering the average hammer price of coins in better condition, an estimated maximum purchase price could be set at a lower range.

Taking all these factors into account, an estimated maximum purchase price for this coin could be approximately 40-50 euros. This is based on the fact that, although the coin has an auction history, its low condition will limit its appeal and value compared to coins in better condition.