By the serial number chronology, the late Charles Semmer produced for his book
Remington Double Shotguns, this gun would be of 1903 vintage. While no production records for the Remington Hammerless Doubles have been found, Charles extrapolated his chronology from surviving shipping records.
The stock cheeks, like the A- to EEO-Grade guns, first appears for a K quality gun in the first 1906 Remington Arms Co. catalog which added the KE-Grade to the line.
1906 Catalog pg 2, K- and KE-Grades.jpg
I see the W.H. stamp in that location on so many guns it must be an inspector in the barrel department. The P you mention is actually a joined JP that I believe is the mark of the rough barrel tube supplier.
Threaded Mode