US Modern Stamps: PNCs

Bryan is not too far away (only have to cross two county lines to get there). Thirty boxes...sounds like something fun to sort through. I've been picking up the mail at the county tax office here in Crockett since October (large volume of mail from then until about February due to payment of property tax).

I have not seen that stamp in my non-profit mail.

That will be different for each different combination of back stamp frequency and PNC frequency.  In the case of the issue you show on your album page, some combinations of backprint and PNC are clearly not possible.  If you want the backprint to be in the middle of a strip of 5 and the PNC to also be in the middle, it's possible that it will never occur on a roll of 3,000.  Imagine the PNC is on the 1st stamp on the roll.  Since it comes on every 14th stamp, it will also be on stamp #15, #29, #43, #57, #71 ... .  If the backprint is on the 2nd stamp on the roll, then since it comes on every 10th stamp it will also be on stamp #12, #22, #32, #42, #52, ... .  No matter how long you look down the coil, you'll never get the backprint to line up on the same stamp as the PNC.

If both backprint and PNC start on an even-numbered stamp on the roll (or both on an odd-numbered stamp) then you'd find the two lining up on the same stamp once every 70 stamps.  (e.g., stamps #1, 11, 21, 31, 41, 51, 61, 71 would have a backprint, stamps #1, 15, 29, 43, 57, 71 would have a PNC.)

And if you're looking for any random location pairing, then let's look at a strip of 5 stamps coming from a random spot anywhere on the 3,000 stamp roll.  First, consider the PNC.  If we use the numbering method above and say that the PNC is on stamp #1 of the roll, then it's obvious that a strip of 5 made of stamps #1-5 on the roll will include the PNC on stamp #1 but a strip made of stamps #2-6 won't have a PNC anywhere - it misses the PNC that was on stamp #1 and it misses the next PNC on stamp #15.  Looking at it that way, a strip of 5 stamps taken from each of the first 14 possible positions on the roll will have a PNC on only 5 out of the 14 strips (a strip starting at stamp #1 has the PNC on stamp #1, and strips starting at stamps #11, #12, #13 and #14 will all catch the PNC at stamp #15).  This pattern repeats every 14th stamp, so 5 / 14 = 35.7% of all possible random strips of 5 will have a PNC.

Now look at the backprint.  Using the same logic, only 5 out of 10 strips will have a backprint on them, or 50%.  If we started with a huge random pile of strips of 5, we have already thrown out all but 35.7% of them because they didn't have a PNC.  Now we need to throw out 50% of all the random strips we have left, because they won't have a backprint.  We're left with 17.9% of the original pile of random strips, or 5 out of every 28, which have both a PNC and a backprint somewhere in a random place along the strip of 5.

But you're picky - you wanted the PNC to be only in the middle position of the strip of 5.  So, 4 out of the 5 strips in our random pile are junk and need to also be thrown out - the PNC will be evenly distributed between positions #1-5 on the strip, but you only want position #3, the one in the middle.  That leaves us now with only 3.6% of the original huge random pile of strips of 5, or 1 out of every 28.

And remember, that is only true for random pairings.  If the printing method used is ALWAYS repeatable and it ALWAYS forces the PNC and the backprint to both occur on even-numbered stamps (or both on odd-numbered stamps), then you get the strip you want 4.3% of the time, or 3 out of every 70 strips - if one is on an even-numbered stamp and the other on an odd numbered stamp (like my example earlier), then it's impossible to have both the PNC and the backprint on the same stamp, and your chances of getting a strip with both of them on it drop to 2.9%, or 2 out of every 70 strips (1 out of 35, if you like reducing the common factors ...).

Ryan

stanley64 wanted to see trans coil errors from my collection, so here we go…

Pics of some of my plate number coil and transportation coil errors, mostly minor miscuts and misperfs. Only two are what I would call a major misperf. 

USA Transportation coil major misperfs errors from my collection

Thanks for the showing philatelia ; those are some real gems there ;-)

Seeing the Stutz Bearcat with its partial number, both top and bottom, as part of a miscut, reminded me of an error from this issue in my own collection,