Thank you Bo!

Is there any way to tell if this person had any military service? The records I have from here in the US, which I know FOR SURE are the right man (naturalization petition, and census), show that he came here at age 19. But family members are INSISTENT that Karl served in the Swedish Navy. I don't know if its true, or if its one of those family stories that people just don't want to let go of (I have discovered others that were not true, such as Karl meeting his wife on the boat to the US).

Does it seem possible that he could have had any naval service prior to emigrating at such a young age?

Where is the best place for me to search for information like this?

Edit to add: his naturalization petition says he was an iron construction rigger, and what info I could find online does seem to indicate that's the kind of skill you could pick up in the navy. But that's not exactly proof, you know?!