Based on the information provided, we know that the coin will be auctioned for the first time and its condition is 25 (BC). Since there are no previous auction data for this coin, we cannot rely on previous prices to make an estimate.

Given that the condition is 25 (BC), indicating a fairly low condition, and the starting price is 40 euros, we could consider that the final auction price might be below this value. However, as it is an auction and there are no historical auction data available, it is difficult to make a precise estimation.

Taking these factors into consideration, and assuming that potential buyers are interested in acquiring the coin at a reasonable price given its condition, we could estimate a maximum purchase price around 30-35 euros. It is important to note that in an auction, the final price will depend on the demand and the willingness of participants to bid on the coin.