Rudy- your .410 is a New Haven (second brand name of Mossberg) Model 183-T.
The Mossbergs had 3 different choke systems. 2 are external chokes that are changeable. The 3rd, which I think you have- is a fixed choke. No, B does not designate the choke- designates the model. Most .410s were made with a full choke. A gunsmith with a choke gauge can tell you in about 30 seconds.
To post a picture here- have pic on your computer. When you are composing a post, look above where you are typing. See the white smiley face? Look to right- see paper clip icon? Click on that, then browse, pictures, find the picture you want, click it once to highlight it, click OPEN, click UPLOAD, wait a couple of seconds, then CLOSE THIS PAGE. Now back to page you are composing, click paper clip again, you get dropdown with file name. click that, should insert the pic.
Sounds complicated, takes 10 seconds once you learn how.
Yours look like this?