Plate Number Coil Stamp Centering

I assume that the centering of the design is the same for sheet and coil stamps. I looked on several PNC websites and found nothing to indicate otherwise, which led to my assumption.

What provoked my question are variations number locations in coils like the 20c Flag which has the number within the design. Then, there are the Transportation coils have numbers partially within the design border, to just below the design, and "dropped plate numbers" that are well below the stamp's design.

Is the location of the plate number is irrelevant to the stamp's centering? Or are there other factors, due to the placement of the plate number, to determine centering for PNCs?

The question you raise came up quite a bit when PNC's first appeared back in 1981. At that time there were two opinions; one camp regarded the plate number as part of the design and others did not. Horizontally the design was supposed to be exactly in the middle - if it was a platenumber strip ( PS ) the joint line should be exactly on the perforations.
Later PNC's do not have a clear joint line any longer; here the design should be centered.
Personally I collect Transportation Coils specialized - I am a 'flyspecker', so centering is less important to me

Peter

I have never seen it mentioned regarding the centering of the plate number itself. I collect PNC's but centering (for any modern material)is not that important to me.

To claim one has an XF condition collection of modern U.S. mint may get one some strange looks.

Angore, I probably read it either in "The Plate Number" or in the very early issues of "Coil Line", but I do remember it coming up quite a bit because the joint line ( at that time sometimes called the "Cottrell Line" ) was usually all over the place.

Peter

Thanks Peter and angora for you comments. I will give a bit more explanation of what I am attempting to find out. The left or right centering is of less concern to me with this post. Nor am I referring to centering of the plate number itself. What I would like to know concerns the vertical centering. The plate number is not part of the design. I need to step back from my comment on the 20c Flag over the Supreme Court. I just checked many online examples and all have the Plt # just below the design border.

I would like to know is this: is the plate number included in the top and bottom vertical centering or is it excluded when determining centering?

OK, that is what I meant by the sentence about the two different viewpoints. Some folks feel that the plate number is part of the design and others do not share that opinion.
If you believe that the plate number is not part of the design - more power to you !
As I mentioned earlier, personally I do not care either way. But some folks sell graded ( !! ) strips on ebay and people seem to buy these.

Peter

You might think differently about a numbered single stamp, but in a strip of 5 you have 4 without the number and only 1 with it and the number is relatively small (particularly for the one or two digit numbers), So the visually effect of the plate number on the centering of the strip is minimal. So I just go with the main design being centered (and then maybe "cheat" just a little to consider the plate number if you want).

Peter - "if it was a platenumber strip ( PS ) the joint line should be exactly on the perforations"
I think this was chosen to make it easy to define horizontal centering, but the fact is the joint line is often not exactly half way between the two stamp designs that are on either side of it, so if you get the line dead center in the perfs, the stamp designs are not dead center between the perfs. It is a tricky situation with no perfect answer.

Sorry to have misunderstood your comment on the two camps. When you wrote "At that time there were two opinions", I took it to mean there are no longer two opinions in our time. My mistake. As for taking the side of those who do not believe it to be part of the design ... well I would expect the plate number to be on every stamp if it were part of the design. Plus, if it is part of the design there would be at least two designs; one with and one without the number. The number would be a deliberate change in the design not an unintended variation. I suppose one could argue successfully for the second opinion. Anyway, not part of the design is what makes sense to me.

If there is no consensus to this day, then one person's VF would be another's F. I'd say that makes its bit messy to grade PNCs.