The actual "Capitan" models (not all tangent sighted HP's are Capitans) imported by Browning and marked "Made in Belgium, Assembled in Portugal" did not have a stock slot. Most "T" & "C" series (mid '60's - mid '70's) also did not have a stock slot cut on their tangent sighted models.
I'm going to have to get a hold of a friend of mine who has a slotted/tangent so-called "Capitan" that, if I recall (yes, I have examined it) was a "C" series.
It looked "factory" to me in that the slot was perfect, and blued.
Unfortunately, he went out and purchased a flat stock for it.
Thanks for the info. I have been under a misconception about modern Hi-Powers all these years.