I recently purchased this shotgun new for a great price. Came with 2 choke tubes in the barrel which I am assuming full top, modified bottom and 3 in a small case. Problem I found is I can't identify any of the choke tubes. I have even looked with a magnifying glass for writing and or rings ( which they mention in the manual ) and I just can't find nothing. Thinking of using my reloading calipers? Any suggestions?