by DARIO DIMARE, 1-20-20

First of all, I want to acknowledge that most of these guidelines were set by N. R. (Woody) Woodward. I just wrote them down. Second is that I also want to acknowledge that there is nothing more exciting than finding an insulator that is a first of its kind or at least unique in some way be it color, embossing, shape, size, or function. I have done it many times and enjoy it as much today as I did the first time. I get equal enjoyment learning something new and filling in some of the informational blanks about the hobby as well. So congratulations on finding a unique insulator or piece of information and thanks for sharing it with the hobby.


  1. ONE is to honor and continue what Woody started and did for most of his life.
  2. TWO is to be honest and fair in all of my assessments, assignments, and decisions.
  3. THREE is to act in the best interest of the hobby.


One should be able to look at one of the many books or guides, and EASILY identify the insulator. You should not have to be an expert to identify your insulator. Although it is not all encompassing, a great way to determine if a new CD should be assigned is to ask yourself, “Can I EASILY tell the difference with my eyes closed?” This helps to eliminate slight curve, slope, or angle differences. The key word here is EASILY!


  1. CONSOLIDATED DESIGN: First and foremost is the definition of the CD acronym. Woody said, “I called it a CD; which stands for CONSOLIDATED Design. If I wanted them to be more refined I would have called them EDs or SDs for Exact Designs or Specific Designs.” He often points out the CD 145 as an example. The CD 145s can be more than 1/2 inch different in width, and almost an inch different in height. Some wire grooves start an inch from the base. Some start 2 inches from the base. Some sides are tapered and some sides are almost vertical. Some domes are round, some are more squared off, and some are nearly flat. But they are all still CD 145s.
  1. INCLUSIVE INTENT: The CD system was meant to be used by non-collectors, beginning collectors, and seasoned collectors. CD identification should be made as easy and understandable as possible. We are not documenting the DNA of an insulator, but rather the Consolidated Design or basic shape. Subtle differences can be dealt with using variants, EIN identification numbers, and specialty books.
  1. CALIBRATION: Calibration and exact measurements are not required. The most basic assignment guideline is that if you have to use a technical instrument, measuring device, or have to “study the book” to determine if it is a new CD then it is NOT a new CD. (See Guideline 1.)
  1. DIMENSION QUANTIFICATION: Another general guideline is the 15% dimension guideline for height and/or width when the height or width is the only significant difference and all else is very similar like a CD 160 & CD 162. If an insulator is not at least 15% different in width and/or height it does not put it up for consideration. And even if it is 15% different, it may still not be assigned a new CD. (15% or more due to underpours, extended skirts, poor factory quality control, nuances, and insulators with wide ranges of heights or widths, do not warrant new CDs under the 15% guideline.)


  1. Different manufacturers or embossings do not warrant a new CD.
  2. Different mold variants do not warrant a new CD.
  3. Intentional manufacturer changes if not a significant difference do not warrant a new CD.
  4. Base configuration and treatment such as drip points, smooth, or round bases do not warrant a new CD.
  5. Color does not warrant a new CD.
  6. Pin hole variants other than threadless/threaded do not warrant a new CD.
  7. The exact location, shape, or thickness of a wire groove or wire ridge does not warrant a new CD.
  8. Function of the insulator does not warrant a new CD.
  9. If we are not sure what it is, it probably does not warrant a new CD.
  10. Minor technical changes, modifications, improvements, or differences do not warrant a new CD.
  11. Slight differences in radii, curves, angles, concavity, flatness, or verticalness do not warrant a new CD.   
  12. Emotion has no place in assigning new CDs.
  13. Value, money, or any other financial motivation does not warrant a new CD.
  14. Precedence of a past CD assignment does not warrant a new CD.


  1. A significantly different design that has not yet been documented.
  2. The existence of a saddle groove.
  3. The existence and/or quantity of an inner skirt or skirts.
  4. The existence and/or quantity of a wire groove or grooves.
  5. The existence and/or quantity of a wire ridge or ridges.
  6. The location of wire grooves or ridges with respect to each other. (Not the location with respect to how far up or down it is from the bottom or top.) For example, a wire ridge above the wire groove is different than a wire ridge below the wire groove and can EASILY be distinguished blind folded, and hence would be a different CD.
  7. The existence of a hole or special feature like a claw, turret, cross-top, or spout.
  8. A good litmus test: Can you EASILY tell the difference between a similar CD with your eyes closed?

I know that Woody has violated almost every rule there is. However, we talked enough for me to understand what unique situations made him violate the rules. Some he wished he could retract. He did not retract them because he did not want to upset the hobby and he did not want to put up with the grief. I will do my best to carry on what Woody started. I am open to all ideas, comments, suggestions and criticism. Please do call or email me.

I get excited when people find new things and information and share their enthusiasm in noting the differences. Without folks digging up new things and sharing them, we would not learn much more and we would grow stagnant. I started collecting insulators in 1967 and do not see an end in sight. 51 years ++++


Happy collecting!


318 Main Street
Northborough, MA