definition of P number

Within ASME:

• P-numbers are assigned to base metals for the purpose of reducing the number of welding procedure qualifications.
• Group numbers are assigned with a P-number to ferrous base metals that have specified impact test requirements.
  

Context is always important, especially with single letters.

In the paper industry, P number refers to the Permanganate number, which is a measure of how much lignin is left in pulp after cooking. The G number or G factor refers to the amount of cellose attack accomplished while cooking wood. The H factor refers to the lignin attack during the cook. All these are very related and important factors in cooking.

I'm going to guess that the first answer was correct for the OP.

I'll be there are a few other P and G numbers in the world that are somehow related.

P&G = Papua New Guinea

Well done poster #1, I would never have guessed from the original post, but I think you got it. Maybe we could ask this guest to submit more quiz questions!

If it is the same P number F number topic you might want to look at

http://cr4.globalspec.com/thread/8421/P-number-G-number-F-Number

or you might find it helpful to do a Mr Google search first to isolate the field of P & N numbers you are seeking.