serialization help

[OH Osthaus]

173612 shows as 28 inch capped pistol grip grade 0 plain twist 12 gauge

[Bill Murphy]

Mark, you are correct. It should be a Grade 1, or PH hammerless.

[OH Osthaus]

Originally Posted by Bill Murphy

Mark, you are correct. It should be a Grade 1, or PH hammerless.

when the book says "PT" - the grade code list in the book shows PT as grade 0 plain twist,

is that meant to say P grade with twist? The "PP" says "grade 1(PH)" with steel barrels?

so both are PH's and the difference is the barrel material?