I came across a similar bell-call system a couple of years ago in a big old Victorian house in Cromer (Norfolk). Some parts of the call wiring had been replaced with zip-type bell wire, but most was the original double-cotton covered wire run in small conduit.

The main panel was located in the kitchen, a glass-fronted wooden box about 16 x 10 inches, with a dozen or more of those "waggley flag" indicators (good description! [Linked Image]). Lifting the front panel allowed access to label the indictaors and revealed the old brass terminals. I'd estimate it was probably installed 1920s.

It was wired to a more modern (circa 1950s) bell transformer and bell, and a couple of the circuits were still working. The owner wanted it left in place, and with a little work we got all but one or two rooms wired to it and working again.

Whether the family that later moved appreciated the fact that the kids could then buzz the kitchen from their bedrooms, I don;t know. [Linked Image]