In most cases the stencil will identify the pipe, (who made it , Where, spec, mfg method, alloy, grade, size, testing, and so on) but the location of the stencil usually has nothing to do with the location of the weld.
There are some specs that require a line or stripe at the ends of each piece that is aligned with the weld. These are done however the mfg desires to do them.
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P.E. Metallurgy, Plymouth Tube