Short form: what is the traditional adhesive used to attach ferrules
to bamboo fly rods, say 40-50 years ago?

Long form: I've got a bamboo fly rod, which originally belonged to my
grandfather. Grampa had a tendency to want to think of himself as a
sportsman, though he actually did very little in the field -- I'm
fairly confident this rod has never been used (I'm a spin-fisherman,
and besides, by the time I got it, it had already been sitting around
without use for long enough I'd be afraid to have a trout on it). It
is, at a guess, 50 years old.

I took it out the other day to show it to my daughter (she fell in
with a bad crowd in Taos and took up fly-fishing), and when I broke it
down again, one of the ferrules came detached from the rod. I'd like
to reattach it, and since its value is entirely sentimental I'd like
to do it with the "right" adhesive, not the best one for the job (else
it would have been epoxied by now!).

Thanks,