Personal opinion, for reference only.
From the physical picture, the production process is indeed relatively rough, it is estimated that it should also be the late Qing Dynasty or Republic of China era of handmade workshop out of the ground. Otherwise, if it is really an antique, your elders will not forget it and should be accountable to you. If it is really a fine work of the ancients, it will be very fine, but this artifact can't be seen. And it wouldn't be something before the Han Dynasty. So the value won't be too great. If it's a bronze artifact before the Han Dynasty, it can be worth tens of thousands; if it's a small bronze thing like this from the Shang Dynasty and before, it can be worth at least a few hundred thousand.
It doesn't matter where it came from. It's been so many years, there's no need to mention how it came to be, just say it was passed down from your ancestors.
The best thing is to let the experts identify its value in person. The identification of cultural relics is a very complex thing, from the picture can only see a rough, can not be completely clear.
If, as you say, it was handed down from the ancestors, it should be a common handmade piece of folklore after the Ming Dynasty. Keep it as a precious souvenir. The lines are slightly messy but very simple, obviously a carp, the symbolism is very auspicious!