channel balances

A contractor from maryland says:
my channel balance is stamped 28 4 CN Caldwell. I feel that the top piece is 19-005 and the bottom is a 15-005 . which would make it a series 380. But when i measure the channel like your diagram, the channel is 29" not the 28 like the stamp says. Which size should i order the 28" or the 29"?

Thank you,
Cameron
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Tom from SWISCO responded:
No, that's right. A stamp doesn't often correspond to the length. A 29" balance like yours would, indeed, have a stamp that starts with the digits 28. As you can see looking at the S380-29, all of our options start with the digits 28, as well.
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