Regardless of the brand, the foundry it was made in, or other markings your dutch oven cookware may have, one thing that is consistent in most are the size numbers.
It would be easy to assume the number on your dutch oven pan is the size or diameter in inches, however this isn’t the case.
It was however back in the old days to be able to order a skillet or pan based on the size to match up with things like the stove eyes (or openings) in wood stoves. These worked similar to the burners we have on our modern stoves – but you could remove the metal eye when you needed maximum heat.
Heat rings, the rims protruding from the bottom of most early cast iron pans, served several functions including as a seal of sorts between the pan and stove eye, as better stability for pans that weren’t perfectly flat on the bottom, and as a way to help reduce hot spots.
Depending on the brand of stove, and the sizes of its various eyes, appropriately-sized pans would need to be purchased for use with it. Or, in some cases, the stove maker also produced pans, which they supplied for use with their units.
Even after gas-fired ranges-- and, eventually, electric stoves-- became ubiquitous, cast iron cookware continued to be manufactured in the sizes and with the designations originally established for its use on wood-burning stoves.
A 1924 Wagner Manufacturing Co. catalog gives these as the bottom diameters of their regular cast iron skillets:
|#2 - 4-7/8"
#3 - 5-1/2"
#4 - 5-7/8"
#5 - 6-3/4"
#6 - 7-1/2"
|#7 - 8-1/4"
#8 - 8-7/8"
#9 - 9-3/4"
#10 - 10-1/4"
#11 - 10-7/8"
|#12 - 11-3/4"
#13 - 12"
#14 - 13"
These were not standard across all companies. A 1918 Griswold Mfg. Co. catalog lists roughly the same dimensions for its regular skillets, with the #3 and #4 being somewhat smaller than Wagner's, and the #13 and #14 somewhat wider. And a Martin #3 skillet is the same size as a Wagner #2. Some manufacturers even went so far as to intentionally make their pans a fraction of an inch wider than those of their competitors, so they could advertise them as being larger.
Things can become more confusing when you start noticing inscriptions like 3B or 8CX, or 710D" or 1053C on pans. The letter or letters after the numbers are what's known as pattern letters. Each model of pan a foundry produced had to have at least one pattern from which to make its molds. Over time, patterns would wear or suffer damage, the result of which would end up being cast into the pan. It was important, therefore, to know which pattern currently in use was creating less than perfect pieces. This provided the solution.
Sometimes you might see a pan with a number that was simply the catalog number.
There is a case in which you may see a small raised number, letter, or group of letters on a pan. These were added to the mold at the time of the casting, and are known as "molder's marks" (as opposed to "maker's marks" which were incised). Since foundrymen were usually paid by the piece, the marks not only helped tally how many pieces a molder made per shift, but also identified whose work was not up to standard. Occasionally, you'll see such marks positioned slightly off-center or askew, testimony to the haste with which they were sometimes applied. Letters tend to indicate a molder; numbers, more likely a foundry shift identifier.
At some point, around the 1950s, manufacturers began to use dimensional descriptions on the pieces, such as 10 5/8 IN. or 6-1/2 Inch Skillet spelled out.
There is still another use for letters, seen employed extensively by Lodge Manufacturing Co. starting in the late 1950s or early 1960s-- as model designations. Although many are self-explanatory, some can be confusing. So, here is a listing of most of them:
AS - All Star Pan
AT - Ash Tray Skillet
B - Breadstick Pan
BE - Bacon & Egg Skillet
C - Cornstick Pan
CAF - Camp Fryer
CB - Corn Bread Skillet
CC - Combo Cooker, Indoor/Outdoor
CF - Chicken Fryer
CK - Country Kettle
CO - Camp Oven
CP - Fluted Cake Pan (Bundt Pan)
CP - Cactus Pan
CS - Chef Skillet
D - Danish Cake Pan
DO - Dutch Oven
DOF - Deep Fry Oven w/cover & basket
DOT - Dutch Oven Trivet
FB - French Bread (2-loaf Vienna Roll Pan)
FBK - Flat Bottomed Straight Kettle
FF - French Fryer w/basket
FP - Fish Pan
FS - Foursome/4-In-1 Skillet Set
GC - Glass Cover
IC - Iron Cover for Chicken Fryer and Dutch Oven
LG - Oblong (Long) Griddle
M - Muffin Pan (6-cup Turk Head)
MP - Melting Pot
NG - Round Griddle, New Style
NTP - No Trump Card Pan
OG - Round Griddle, Old Style
OS - Oval Serving Griddle
P - Popover Pan
PP - Perch Pan
RBK - Round Bottomed Straight Kettle
SC - Skillet Cover
SK - Skillet
SP - Sauce Pan or Stew Pan
SQSK - Square Skillet
TB - Top of Stove Broiler (Axford style skillet)
TK - Tea Kettle