Serial Numbers

[Ngchen]

I was working on my Trek 7100, and noticed that there were TWO numbers stamped into my bottom bracket. I know frames are supposed to be numbered for registration purposes and to stop thieves, but what's the deal with two numbers being present?

[Zinn-X]

maybe your frame is a super limited edition?

[John E]

I have seen frame size, model designation, and lug angle stamped into bottom brackets.