I have an old K&T meter as office cha cha, two little holes in, two out. This came from an exposed situation one could walk up to.
In fact, much of the first 'wired after it's built'places in New England had exposed K&T
my code book collection only goes back to the 50's, so i'm just guessing that any exposed to physical damage references may not have existed
much of the K&T run back then was in wooden wiremould, but some of it, for instance in grange halls , or manufacturing shops, remained exposed on porcelian knobs or porcelian tubes
my take is the issue was more esthetic than anything else
in fact, the old mill being renovated in Springfield VT had exposed tubes with an I.D. of over 1" for fat copper 3phase conductors , which they just tapped off of into fuse-only museum worthy panels
~S(land code forgot)parky~
