Norweigen Fishing painting

My mother is in the process of clearing out and selling her house. One of the items that she gave us is a painting. She never cared for it much, but my father claimed that it may be valuable. It was bought by my grandfather, but I don't know when ( he died in 1965). The painting is of some fishermen and fishing boats on a rocky, sandy shore. It measures roughly 42"x29" in the frame. The signature at the bottom is N Ulfsten 1883. My grandfather was from Norway. Looking online, I am guessing that the painter is Nicolai Martin Ulfsten. I am wondering how to determine it's value to see if it may need to be insured.