Bill,
As I had visited this relay/switching building in the mid 1970's even if they
had changed over to solid state switching, would the fuse wire still be used
for fusing the lines going out to customers ?
IIRC that was what I was told it was for.
IIRC I was last on the 'tip and ring' around early 1980's, and even then only put on a toolbelt when we had an emergency and not enough craft warm-bodies. Or the Loma Prieta quake, when I sent all the locals home to see to their families and single-handed the site meself for a day or so..
Protective devices - subscriber loop, or any other plant - were already modern, modular, snapped in as blocks, did a great deal more in the way of useful 'stuff' than a bit of fusible wire could even dream of. Mind - I was with a Telco many called "Gold Plated". Cable & Wireless.
The site you recall wudda been already over-age-in-grade with those legacy systems even for "extract the last erg of value from every penny of plant" Ma Bell & chillin's.
As they were THEN, anyway.
Was it one of the NON Bell Local Exchange Carriers, perchance?
Bell system only ever did hold around 50% of the industry. GTE had the next biggest single chunk, and within a decade or so of Carterphone Big Bang, we had over 800 long-distance "players".
Only a few were 'facilities' based. Held actual wire, fibre, microwave, satellite - physical transport resources, IOW.
The rest were just reselling carriage over networks of the majors and of each other.
Bill