Looks very similar to a Martin Roadrunner, especially the fronk forks.Looks like it had a chain-drive gearbox. Go to mikeybike.com then to Restoration in progress. should be fourth pic down.Ray
You've got a good mystery going here. I think we can say for sure it is a Martin Roadrunner fork, as Martin offered the front end to shops and sold many of them for 26" bicycles. All of the Roadrunner frames I've seen had a large gusset attached to the head stock and the backbone and down-tube were a continuous loop from the headstock gusset down and back again. Your bike has neither the large gusset nor the continuous loop frame. The rear forks of the Roadrunner were also of a loop design, whereas your bike is not. Roadrunners also mounted the seat via a 3 point contact, whereas your's mounts via a seat post. Roadrunners also had a kick-stand that swung off the right of the bike, often with a band brake/peddle on the right side too. All the Roadrunners fit with Whizzer engines were push-start bikes since the Roadrunner had no peddle crank.
Roadrunners were offered in a wide variety of offerings - H model Whizzer kits with belt drive, Marman Twins with chain drive, Albion 2- and 3-speed transmission models, B&S rope-start models, as well as a rolling chassis with no motor.
All that said, your bike looks like it was chain drive, so perhaps fitted with an Albion tranny once upon a time, and appears to have plenty of room for such an accessory. The frame looks partially like a Martin but seems to lack many of the distinctive features of a Martin as described above. Keep us posted if you figure out more about it.