When London Regional Transport ran public transport in London there used to be an 'LT Card' which was basically valid on the tube and bus services. However I seem to remember that it wasn't valid north of Queens Park on the Bakerloo Line because National Rail fares applied between Queens Park and Harrow & Wealdstone.
Just to confuse things further we also had Travelcards which were valid, as now, on trains, tubes and buses in the relevant zones.
The original Travelcard was a London Transport only product - when a version was introduced that covered British Rail services, it was called Capitalcard and was more expensive. The two products were combined around 1990, with the LT Card appearing a few years later that was the same as the original Travelcard product.
I can't see a TfL only product being reintroduced now the ticketing systems throughout Greater London are so integrated, and with the large number of LO routes that share stations with other franchises operators