This is an Airline version of Harmony's H-78. This model was sold under a lot of different names, among others Harmony, Airline, Silvertone, Barclay and Heathkit (as a DIY kit).
The H-7x series was available as the H-75 (sunburst), H-76 (sunburst, Bigsby), H-77 (cherry sunburst), H-78 (cherry sunburst, Bigsby), S-1429 (early Silvertone version) and S-1454 (later Silvertone version w/Bigsby)
This guitar has "moustache" pickups instead of the usual "maximum" PU's.
The 3 pickup H-7x series was among the high-end Harmonys.