Have a red DuoFold Jr, Pat. 4-25 on barrel.

The nib says Parker, line below a curved DuoFold, next line says Pen... then below the word Pen is the letter "P"

What's the "P" mean?

Stands for where the pen or nib was made, I think. Not too sure.

Good Question. I don't know that it has ever been stated what the P (or other letters that appear there) mean other than they may identify a location or lot or time that the nib was made to help identify returns and problems with production.

I have never heard another explanation that definitively states what they stand for.

N's on English Parkers do refer to the Newhaven Factory, though.

Phil