The primer in question was more likely Bert Weedon than Bert Jansch.

Lots of instrument tutors from the early 20th century survive. (As I work in the antiquarian book business, a lot of them pass through my hands, mostly on one-way trips to the recycler). But the guitar is one of the least commonly encountered. Ukulele, banjo, piano, harmonium, brass and anglo concertina were vastly more popular.

A working class musician in Victorian Britain was much more likely to play a brass band instrument than anything else. (South-East Scotland had a tradition of miner fiddlers - I don't know how common that was elsewhere).

Like I said, look at old newspapers. It's obvious from the ads which instruments were available and visible, and the guitar wasn't one of them.