I have a four digit rifle that appears based on all I can read from Arthur Pirkle to be correct except for a later sight elevator and finish has been added to the wood at some point.  This rifle is 32-40 most bluing worn to a silvery patina evenly, proper striations showing on the reciever. These are the questions Im trying to answer- 1st the barrel is 21”  trying to figure out if it was just done by a very good gunsmith or possibly at the factory- the front sight dovetail is correct @ 11/16 from the muzzle, the distance from the muzzle to the magazine cap is correct @3/16, the distance from the muzzle to the magazine tube slot is correct @3 1/2”.  Is there any way to determine is this could have been done at the factory? 

2nd- upper tang marking is a type 1- which supposedly ended sn# 3000

3rd- reciever has niether the “10 o’clock” hole upper left of the loading gate typical of the 1a recievers from this sn range or the 12 o’clock screw of the later 1b  recievers… 

any info or suggestions greatly appreciated. It is a nice rifle, spent its life on a ranch in British Columbia before being rehomed