Lyman
I would go to browning .com.They have a link to serial numbers on the sight that should help you.
Your Browning .380acp was one of the last guns made in the year 1965.That year the last serial number was 598804.It should also be noted that the Browning 380 was redesigned due to the gun control act of 1968.This new model came out in 1970 with a longer barrel,adj.rear sight,and modified grip.
Savage 325c rear peep?
None
It is possible.
Requires appraisal
The thread size is: M3.0-.5 The Browning part number for the bead is B1116580
I would go to the Williams gun sight company.They should have a chart that will answer your question for you.
3x0.5 thread
Don't alter your BLR by drilling holes in it. Instead, find a receiver sight that utilizes the existing scope mount holes in the top of the receiver. Extra holes are unsightly and they destroy much of the rifle's resale value, especially to collectors. It is best not to make permanent alterations to a firearm such as yours. That's my answer.
Try e-gunparts.com, Midwest Gun Works, Browning.
im pretty sure you sight it in like every other scope as long as you keep the parellax in mind. sight in at 75 yards