This is a bit long. If it's not appropriate for this thread, let me know and I'll severely edit or delete it, if possible.
C.N.
Pattern Numbering System
The basic pattern number consists of six digits. Think of them
as two sets of numbers of three digits each. The first three digits
relate to the knife's construction materials. The first digit refers to
the handle material. The second digit refers to the number of blades
in the knife. The third digit refers to the material composition of the
bolsters and liners of the knife. The last three digits are the
designated number of a particular handle-die shape, or the individual
style of a particular knife. When Robeson began numbering their
knives, they started with 001. They continued to number the knives
up into the 900's. As older styles of knives were discontinued
because that type knife no longer had a market, they reassigned
that knife's number to a new style of knife. One example of that is
a swell-end, two blade "Harness Jack" with a spear master blade and
a leather punch and the handle-die number
382. With the invention of the automobile, and the power tractor,
the use of horses and therefore horse harnesses, greatly diminished.
They discontinued the Harness Jack. They later reassigned that
number to a relatively modern and very attractive two blade
Trapper pattern.
One will find Robeson knives with only a five digit pattern number.
This occurred for one reason. If the handle-die shape number was
between 010 and 099, sometimes the first position zero was dropped
from the pattern number, creating a five digit number. The number
was actually still the same, if one continues to treat the numbers
as two separate sets of numbers.
For instance, if a 626056 regular jack was marked, 62656, the
number is the same and should be read as, "626 / 56" and the longer
number as, "626 / 056".
Most of the examples of five digit numbers occurred on knives
with smaller master blades where a six digit number did not fit well.
During the 1950's, Robeson imported some German made
pocketknives. All the examples I've seen had four digit pattern
numbers. An example is a six blade utility knife, much like some
Swiss Army Knife patterns, and has the number, 4864.
Knives will be seen with a suffix added to the pattern number.
"1/2" and "1-2" are the same, and mean "One-Half". I've noticed
that usually occurs on knives that normally have a clip master blade,
but instead have a spear master blade, or some other variant of
blade configuration. Tom Kalcevic, in
Knives Can Talk,
states that knives with an added bail carry the suffix, as well.
Other suffixes I've seen are 50, 85, 100, 125, and 250.
I do not know enough to know what they mean, exactly.
The first digit of the Robeson pattern number denotes handle material.
The known numbers are as follows:
0 = Metal (Aluminum, nickel-silver or Stainless Steel)
1 = Ebony, Black Cocobola Wood, or Black Composition
2 = Rosewood, or Walnut
3 = Slick Black Composition
4 = Ivory Celluloid
5 = Saw Cut Bone, Genuine Stag, Saw Cut Delrin, or Gold-Filled Metal
6 = Genuine Bone, Jigged Rough Black Plastic, Jigged Delrin Imitation
Bone
7 = Genuine Pearl or Abalone
8 = Single Colored or Multi-Colored Patterned Celluloid, other than black
or ivory
9 = Imitation Pearl Celluloid, Christmas Tree Celluloid, ShurWood, or
Gun Metal
C = Older Celluloid Knives
G = Gold
The oldest Robeson knives have green bone handles, followed
by brown bone with different qualities of dies and jigging patterns,
then the famous strawberry bone of the 1950's.
The second digit of the Robeson Pattern number denotes the
number of blades. The known numbers are 1 through 6.
The third digit of the Robeson pattern number denotes the material
composition or combination of materials used for the liners and bolsters.
The known numbers are as follows:
0 = Combination Handle, Liners, and Bolsters
1 = Steel Liners and Bolsters
2 = Brass Liners and Nickle-Silver Bolsters
3 = Nickle-Silver Liners and Bolsters
4 = Not known, but seen on at least two knives, one a 234322
take apart slot knife.
5 = Special
6 = Again, Brass Liners and Nickle-Silver Bolsters
8 = Integral Nickle-Silver Liners and Bolsters
9 = Stainless Steel Liners and Bolsters
Now, let's look at that 626056 pattern knife I mentioned earlier.
The knife under discussion is a 3 3/4" regular jack knife.
The first digit, 6, denotes bone handles, or possibly jigged rough
black plastic or jigged Delrin imitation bone, depending on when
the knife was manufactured. The second digit, 2, denotes two
blades. In the case of this particular pattern, there is a clip master
blade and a large pen secondary blade. The third digit, 6, denotes
brass liners and nickle-silver bolsters. The last three digits, 056, is
the designated Robeson number for that particular 3 3/4" regular jack.
Simple, Huh?