How to Identify Vintage Cast Iron: Gate Marks, Heat Rings and Numbers

Turn the pan over. The three things worth reading, in order, are: a raised scar or slash across the bottom (a gate mark, which dates the piece to roughly pre-1890), the raised ring around the outer base (the heat ring, whose style and notching narrows the maker and era), and the numbers and letters (a size number that is nota diameter, plus pattern letters and molders' marks). A pan with no brand name is not a dead end — those three features carry most of the information.

This is the identification companion to our vintage buying guide, which covers where to hunt and what to pay. Here we are only concerned with reading the object in your hand.

1. Gate marks: the single clearest dating feature

A gate mark is a raised line, slash or scar running across the bottom of the pan — often a couple of inches long, sometimes stretching across the whole base. It is not damage. It is the remains of the gate — the channel molten iron was poured through in a sand mold — snapped off and ground back after the casting cooled.

Bottom-gated casting was standard through the 1800s and American foundries largely abandoned it around 1890 in favor of side-gating, which leaves no mark on the cooking surface side. The Cast Iron Collector places gate-marked cookware in the late 18th or 19th century, noting the technique persisted into the 20th century on large-format items like sugar kettles.

So: a gate-marked skillet is genuinely antique — call it 130 years old or more. That is the strongest single dating signal on an unmarked pan, and it usually beats everything else on the piece.

2. Heat rings

The heat ring is the raised ring around the outer edge of the base, designed to sit on a wood-stove opening. Its presence tells you the pan predates the smooth-bottomed era; its style can narrow the maker considerably.

The Cast Iron Collector's identification notes give a set of patterns worth memorizing:

• Full, unbroken inset ring— associated with Birmingham Stove & Range and early Lodge.
• Single notch, opposite the handle at 12 o'clock — Lodge, 1930s.
• Three notches, at 9, 12 and 3 o'clock — Lodge, 1940s to 1987.
• Outside heat rings— Vollrath and some Chicago Hardware Foundry pieces.
• Smooth bottoms, no ring— later pieces generally, and characteristic of Wagner and Griswold.

A pan can carry both a gate mark and a heat ring. That is normal, and the gate mark is the one doing the dating.

3. The numbers, and the myth about them

The large raised numeral on the handle or the base is not the pan's diameter in inches. This is the most widespread piece of misinformation in the hobby. The numbers correspond to stove eye openings on wood-burning stoves.

From a 1924 Wagner catalog, the actual bottom diameters were roughly: a No. 3 at 5½ inches, a No. 6 at 7½ inches, a No. 8 at 8⅞ inches, a No. 10 at 10¼ inches. Griswold's dimensions varied slightly — some manufacturers deliberately made their pans a fraction wider than competitors'.

This matters practically: a “No. 8” skillet is close to a modern 10-inch pan at the rim, not an 8-inch one. If you are shopping vintage and sizing against your modern pans, measure across the top instead of trusting the number. Our skillet sizes guide covers modern sizing.

4. Letters: pattern letters, molders' marks and model codes

Pattern letters— a letter following the size number, as in “3B” or “8CX”. Popular sizes had several working patterns in use at once, each given a letter so a foundry could trace which pattern produced a bad casting. The Collector's honest note is that collectors do not care what pattern letter a piece carries unless they are collecting one of each for fun.

Molders' marks— small raised letters or numbers added to the mold at casting, identifying an individual molder or a shift for productivity tracking. On Lodge pieces these often appear at the 6 o'clock position.

Model codes— letters denoting the type of pan. Lodge began using these in the late 1950s: SK for skillet, DO for dutch oven, C for cornstick pan. If you are holding a Lodge piece specifically, our Lodge dating guide works through the sequence in detail.

5. Handles and other tells

Handle shape is a genuine attribution signal once you have seen enough pieces. The Collector singles out Griswold's “Iron Mountain” line (1930s to early 1940s) for its untapered oval handle opening, and Vollrath for a hollowed-out handle underside with a long reinforcement rib running to the hanging hole. Raised size numbers on top of the handle appear across many makers.

What you often cannot know

Be prepared for an honest dead end. Unmarked pieces from small 19th-century foundries frequently cannot be attributed to a manufacturer at all. Regional foundries were numerous, branding cookware was not yet standard practice, and no register of their patterns survives. A gate-marked, unmarked skillet may be datable to an era and never to a maker.

That is not a failure of your research. It is the actual state of the record, and anyone selling you a confident attribution for an unmarked 1870s pan is guessing.

Read it before you clean it

One practical warning. Wire wheels, angle grinders and aggressive sanding soften raised lettering and can erase a molder's mark entirely. If a piece might be identifiable, strip it chemically — a lye bath for the grease and electrolysisfor the rust — because neither removes metal. Photograph the base before and after.