Gonna take a stab at this.
If memory serves, barrels
up into the seventies on "those"
guns were pinned where the barrel
and receiver met. I'm looking at an
older pinned kit gun. It was,presumably,
to keep it from backing out.
When that company began looking at its
bottom line, and certainly that applies
to the multiple ownership changes in the
eighties, it determined the pin wasn't
needed. Quality control went to hell
during those transition years.
My guess is that the pinned models are
percieved as having been made when "the
firm" took pride in workmanship.
Anyone else care to take a shot at this one?