We know that most of the stamped sheetmetal parts received a code for the plant and week that the part was stamped, but we don't have a full list of which plant used which code. If you know of more, please post.
H - Hamilton Ohio. About 15 miles from Norwood. Stamped quarter panels, doors and hoods. Pretty sure on this one.
K - Kalamazoo Michigan? Maybe not. That's about 300 miles away from Norwood.
T - Taylor-Tedford ? Wild guess on this one. Or maybe Fisher Body Tank Plant. Grand Blanc, Michigan.
https://www.camaros.org/numbers.shtml#sheet
I've never seen a list of stamping plants. But I asked AI. I wouldn't put much weight on this. There were lots of small stamping plants not listed, like Hamilton and Mansfield until I specifically asked.
Major GM Metal Centers & Stamping Plants active during this era include:
• Flint Metal Center (Flint, Michigan) – Opened in 1954; produced major sheetmetal stampings for GM models.
• Parma Metal Center (Parma, Ohio) – Opened in 1948; manufactured sheetmetal stampings and sub-assemblies.
• Marion Metal Center (Marion, Indiana) – Opened in 1956 (originally a Fisher Body division plant); stamped sheetmetal parts and blanks.
• Pontiac Metal Center (Pontiac, Michigan) – Operated as a metal fabricating facility producing sheetmetal stampings.
• Kalamazoo / Comstock Fisher Body Plant (Comstock Township / Kalamazoo, Michigan) – Ground broken in 1964 and production began in August 1965 as a major modern Fisher Body metal fabricating plant.
• Wyoming Metal Center / Grand Rapids Stamping (Wyoming / Grand Rapids, Michigan) – Major Fisher Body/GM stamping complex expanding heavily through the 1960s and 1970s.
• Indianapolis Metal Center (Indianapolis, Indiana) – Fabricated stamping dies and metal parts.
- Mansfield / Ontario Metal Center near Mansfield, Ohio, which opened in 1955.
- Hamilton / Fairfield Plant in Butler Co OH.
Taylor-Tedford - I saw that post about that stamping mark too. Not sure how they came up with it, but whatever the name of the stamping facility, it wasn't GM. And thus wouldn't use the GM format.
Thanks. Somebody out there knows. Maybe I will ask in one of the Fisher Body online groups. I had done that maybe a year ago but nobody ever responded.
Another AI search yielded this.
Stamping dies contained removable steel inserts that pressed a "run number" into hidden flanges, inner door skins, trunk lids, and quarter panels to verify full press closure and track production batches.
• First Letter(s) (Plant/Die Code): Identifies the Fisher Body stamping facility or specific press line (such as H, K, T, W, or Z).
• Following Two Digits (Production Week): Indicates the calendar week of the year the panel was stamped (for example, H18 means the panel was stamped at Hamilton during the 18th week of the year).
• Trailing Numbers (Shift/Die Info): Some panels include an additional digit or letter representing the shift or specific press die cavity.
And then found this about the letter T but I have no idea if it is true.
T — Tarrytown, New York (or Tonawanda/Regional Press): While T frequently appears as a press die code on trunk lids, doors, and quarter panels, GM never released a complete public master key for internal press-die plant letters.